{"paper_id":"134d0540-0c42-4db9-a598-373eab46bbaf","body_text":"Experimental Investigation of the Properties of Collapsible Soil Stabilized by Colloidal Silica | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Experimental Investigation of the Properties of Collapsible Soil Stabilized by Colloidal Silica Fatemeh Bakhshandeh, Reza Noorzad, Bahram Ta'negonbadi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6655792/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 16 Aug, 2025 Read the published version in Scientific Reports → Version 1 posted 10 You are reading this latest preprint version Abstract Collapsible soils pose significant geotechnical challenges due to their tendency to exhibit high strength under natural moisture conditions but undergo substantial settlement upon wetting. To address this issue, various stabilizing agents, including lime, cement, silicates, resins, and acids, have been explored. This study investigates the effectiveness of colloidal silica (CS), a low-viscosity solution capable of forming a gel, as a stabilizing agent. Its unique properties enable it to be injected into or mixed directly with soil, offering versatility in application. The behavior of CS-stabilized collapsible soil was evaluated through collapse potential and unconfined compressive strength (UCS) tests. Scanning electron microscopy (SEM) was also conducted to analyze microstructural changes in untreated and CS-treated soils. Colloidal silica was added at concentrations of 3, 5, 7, and 10% by weight of dry soil, with curing times of one, 7, 14, and 28 days. Collapse potential tests were performed at relative compactions of 80 and 85%, while UCS tests used a relative compaction of 95%. Results indicated that colloidal silica significantly reduced soil collapsibility while enhancing stiffness and UCS without inducing brittleness. A 5% CS concentration was optimal, reducing collapsibility from severe to negligible. Increased relative compaction (80 to 85%) further decreased collapsibility, whereas higher inundation stress increased it. These improvements are attributed to pore filling by colloidal silica, which enhances inter-particle bonding and structural integrity. Physical sciences/Engineering/Civil engineering Physical sciences/Materials science/Structural materials/Mechanical properties Colloidal Silica Collapsible Soil Soil Stabilization Collapse Potential Unconfined Compressive Strength Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 1. Introduction Several factors, including rainfall, rising groundwater levels, and human activities such as washing and irrigation, contribute to an increase in soil moisture content (Mahmood and Abrahim, 2021 ). The partial or complete wetting of moisture-sensitive soils results in either collapse or swelling. Consequently, an increase in soil moisture content can lead to volume changes, thereby reducing both bearing capacity and shear strength. As a result, this issue presents a significant challenge in the design of foundations, both during and after the construction of engineering structures (Al-Obaidi et al., 2013 ). Collapsible soil is characterized as unsaturated soil that can endure relatively high pressures without exhibiting significant changes in volume; however, it is susceptible to abrupt and substantial volume loss upon an increase in moisture content (Cerato et al., 2009 ). Collapsible soil is, in fact, a moisture-sensitive soil that undergoes a reduction in volume as moisture content increases. If such soil is not treated prior to construction, subsidence resulting from soil collapse can lead to significant financial costs (Houston et al., 2001 ; Rollins and Kim, 2010 ). Several methods have been proposed to minimize or eliminate soil collapsibility. The selection of the most suitable method depends on factors such as the depth of the collapsible soil, the type of structure, its cost, and the feasibility of the method (Houston et al., 1995 ). Chemical stabilization is one of the oldest and most widely used methods for soil improvement, typically involving the mixing of soil with one or more types of additives. Various materials, including lime, cement, silicates, resins, and acids, have been employed to stabilize soil (Fang, 2013 ). Sodium silicate has been utilized as a chemical slurry for injection into the soil; however, colloidal silica presents a suitable alternative due to its low viscosity (Bolisetti et al., 2009 ). Colloidal silica is a solution that undergoes gelation when sodium chloride is added or its acidity is altered. Consequently, it can be injected into the soil or mixed with it, ultimately filling the voids within the soil upon gelation (Persoff et al., 1999 ; Lin, 2006 ). Permeation grouting involves injecting a low-viscosity slurry to fill voids within the soil. Cement grouts, due to their high initial viscosity and large particle size, require high injection pressures to permeate the soil. In contrast, chemical grouts are easier to inject due to their lower initial viscosity compared to cement grouts; however, they are often more expensive and may contain toxic compounds. Colloidal silica, on the other hand, offers the advantage of a low viscosity (similar to water) and very fine particles, while also being chemically non-toxic (Pedrotti et al., 2020 ). Nowadays, colloidal silica, as a preferable soil stabilizer increasingly used (Georgiannou et al., 2017 ; Kakavand and Dabiri, 2018 ; Wong et al., 2018 ; Noorzad and Nouri Delavar, 2019 ; Krishnan et al., 2021 ; Seif et al., 2024 ). The colloidal silica (CS) lead to decrease collapsibility and increase strength and durability of the soil. Additionally, its use does not harm the environment (Krishnan et al., 2021 ). The useful life of colloidal silica exceeds 25 years, whereas the useful lives of sodium silicate and acrylic grout range from approximately 10 to 20 years. The cost of colloidal silica at a concentration of 5% by weight is estimated to be comparable to that of microfine cement. Furthermore, the expenses associated with colloidal silica injection are significantly lower than those related to cement injection (Gallagher et al., 2007 ). Wong et al. ( 2018 ) conducted a series of one-dimensional consolidation and shear strength tests to investigate the behavior of sand and kaolinite clay stabilized with colloidal silica. Their findings indicated that the addition of colloidal silica significantly enhances the stiffness and peak friction angle of the sand. Furthermore, the consolidation tests revealed that the stabilized clay exhibited a lower void ratio compared to the unstabilized samples during the initial stages of testing. Additionally, it was observed that the settlement rate of the stabilized clay remained low under vertical stresses below 30 kPa; however, as vertical stress increased, the settlement rates for both the stabilized and unstabilized samples converged. Krishnan et al. ( 2021 ) investigated the static and dynamic behavior of colloidal silica-stabilized sand. The findings from their study indicated that the optimal concentration of colloidal silica for relative densities of 30%, 40%, and 60% is 12.5%, 11%, and 10%, respectively. The increased cohesion in colloidal silica-stabilized sand was attributed primarily to the specific surface area of the colloidal silica particles and the formation of siloxane bonds. Additionally, the results from dynamic experiments demonstrated that the application of colloidal silica at the optimal concentration effectively reduces the tendency for liquefaction. Most of the past studies performed on the CS treated soil, have mainly focused on the sand, silty sand and sandy clay (Georgiannou et al., 2017 ; Kakavand and Dabiri, 2018 ; Noorzad and Nouri Delavar, 2019 ; Krishnan et al., 2021 ; Seif et al., 2024 ). Few studies have been performed on clay (Wong et al., 2018 ). Furthermore, no research has been conducted to examine the collapsibility and strength characteristics of colloidal silica-stabilized collapsible soils, specifically loess soils (CL). The main purpose of this research, was to evaluate the influence of various contents of CS on the collapsibility, compaction properties and unconfined compressive strength (UCS) of loess soils. Also, the effect of relative compaction and aging on the collapsibility and strength properties of CS-treated and untreated collapsible soil was investigated. Additionally, the findings of this study were enhanced by conducting a microstructural analysis of the base soil both prior to and following stabilization, utilizing a scanning electron microscope (SEM). 2. Experimental investigation 2.1. Materials 2.1.1. Clay (CL) Considering the prevalence of collapsible soils in Golestan Province, the soil utilized in this study was sourced from the construction site of the Golestan Dam, situated 12 kilometers northeast of Gonbade Kavous city, Iran. Figure 1 shows the grain size distribution of the studied soil that was determined using sieve analysis and hydrometer test according to ASTM-D6913 (ASTM, 2017) and ASTM-D7928 (ASTM, 2017). Based on the results of the Atterberg limits tests conducted in accordance with ASTM D 4318 (ASTM, 2017), the liquid limit and plastic limit of the soil were approximately 27% and 17%, respectively. This classification identifies the soil as low plasticity clay (CL) according to ASTM D 2487 (ASTM, 2017). The compaction test, performed following ASTM D 698 (ASTM, 2021 ), indicated that the optimum water content and maximum dry unit weight of the soil were 15.06% and 18.09 kN/m³, respectively. Furthermore, the specific gravity was measured at 2.71, determined using ASTM D 854 (ASTM, 2014). 2.1.2. Colloidal silica (CS) The colloidal silica employed in this study was produced by Dr. Khan Company, India. The properties of this product are detailed in Table 1 . Figure 2 illustrates the colloidal silica before and after gelation. In this study, the required volume of concentrated solution (30% by weight) to prepare more dilute solutions (3, 5, 7, and 10% by weight) was determined according to the following equation: Table 1 Characteristics of used colloidal silica in this research Weight percent of silica (%) Particle size ( \\(\\:\\text{N}\\text{a}\\text{n}\\text{o}\\text{m}\\text{e}\\text{t}\\text{e}\\text{r}\\) ) pH Density (gr/ml) Viscosity (Centipoise) 30 10–14 8.5–10 1.19–1.21 7 $$\\:{V}_{1}=\\frac{{C}_{2}}{{C}_{1}}{V}_{2}$$ 1 In which, C 1 : Concentrated solution concentration, C 2 : Concentration of the desired dilute solution, V 1 : Required volume of concentrated solution and V 2 : Volume of desired dilute solution. Based on the experimental results, the gelation time of the colloidal silica solution employed in this study was determined to be approximately two hours. 2.2. Laboratory tests Laboratory tests including collapsibility potential and UCS was performed with different percentages of CS. In order to clarify the results, SEM analysis was applied to trace the microstructural changes. Stabilized soil samples for this experimental research were prepared using four percentages (3, 5, 7 and 10%) of CS by soil dry weight. 2.2.1. Collapse potential test The effect of CS on the collapsibility of stabilized soil was investigated by conducting a collapse potential test based on ASTM D 5333 (ASTM, 2017). To prepare stabilized samples, at first, the required dry soil weight is determined based on the volume of the mold (consolidation ring), the desired relative compaction and the obtained results from the standard compaction test. The quantity of colloidal silica necessary for sample preparation is determined based on the target moisture content (optimum moisture content). This process involves calculating the volume of water needed to achieve the desired moisture percentage in the soil while taking into account the concentration of the colloidal silica solution (3, 5, 7, and 10% by weight). Consequently, the amount of the colloidal silica solution with the specified concentration is computed accordingly. Concentrated colloidal silica (30% by weight) is combined with a sodium chloride solution containing the requisite water for diluting the colloidal silica solution, and the necessary sodium chloride particles, to provide a sodium chloride solution of the desired normality. Then the resulting colloidal silica solution is mixed with the required amount of dry soil. According to the research conducted by Noorzad and Pakniat ( 2016 ), the relative compaction of undisturbed samples obtained from the Golestan Dam construction site is 80%, therefore, the collapse potential investigation is conducted with a relative compaction of 80%. Also, to investigate the effect of relative compaction on collapse potential, samples with a relative compaction of 85% were also made. Immediately after preparation of a homogenous mixture from the soil and colloidal silica solution, the resulting mixture was compacted in 3 layers using static compaction to prepare the uniform samples (50 mm diameter by 20 mm height). After compaction of any layer its surface was scarified about 3 mm to reach the fair bond. Then, the compacted specimens were sealed in a double layered plastic wrap and kept in a room with controlled temperature under various curing times. (1, 7, 14 and 28 days). 2.2.2. Unconfined compression test The effect of the additive on the enhancement of shear strength in treated soil was examined through unconfined compressive testing, conducted in accordance with ASTM D 2166 (ASTM, 2024). To prepare stabilized specimens, the materials are initially mixed in a manner similar to that described in the previous section. However, it is important to note that the quantities of materials required are tailored for specimens measuring 50 mm in diameter and 100 mm in height, with a target relative compaction of 95%. The recommended compaction of fine materials used in an embankment for the majority of construction projects is between 95 and 100% of the maximum dry unit weight (MDUW) (Ta'negonbadi and Noorzad, 2017 ). Consequently, a target dry unit weight of 95% MDUW was selected for the samples utilized in these tests. Immediately following the preparation of a homogeneous mixed of soil and colloidal silica solution, the resulting mixture was compacted into five layers using static compaction to create uniform specimens measuring 50 mm in diameter and 100 mm in height. According to the research performed by Ta'negonbadi and Noorzad ( 2017 ), to assess the uniformity of the samples, several specimens were fabricated and each was subsequently cut into 6 to 8 segments using a narrow wire saw. The weight and volume of each segment were then recorded. Ultimately, the unit weight and density of each segment were calculated, revealing that the variation in density along height of the sample from the target density was negligible. Consequently, the prepared samples can be regarded as uniform. Once the initial setting time has elapsed, the sample is extracted from the mold using a jack and subsequently stored in a double layered plastic wrap until the specified curing time is reached. 2.2.3. Analysis of microstructure Scanning Electron Microscopy (SEM) analysis was conducted on both CS-stabilized and unstabilized soils. Based on the findings from the SEM analysis, the stabilization mechanisms of the stabilized specimens were examined, and the observations obtained from the tests were elucidated. 3. Results and discussion 3.1. Test results of determining the collapse potential and index The test results for determining the collapse potential and collapse index are presented in Tables 2 – 6 . The parameters examined in these tests include: Table 2 Test results of collapse index and potential of untreated samples Relative compaction (%) Inundation stress (kPa) Collapse index (%) Collapse potential 80 100 4.39 Medium 200 7.27 Relatively severe 400 8.87 Relatively severe 85 200 4.15 Medium 400 5.33 Medium Four different concentrations of colloidal silica (3, 5, 7 and 10% by weight) Two relative compactions for the collapse potential test (80 and 85% of MDUW) Four curing times (1, 7, 14 and 28 days) The effect of each of the above parameters on the behavior of stabilized samples is examined separately hereunder. 3.1.1. Effect of relative compaction on the collapsibility As the results of the tests of collapse potential under a stress of 100 kPa show, at this stress level, the collapse potential for specimens stabilized with a relative compaction of 80%, decreases to an acceptable value. For this reason, the effect of relative compaction at this stress level is omitted (refer to Tables 2 – 6 ). According to Table 2 , it is observed that with increasing the relative compaction in unstabilized samples, the collapse index decreases. So that with increasing the relative compaction from 80 to 85%, the collapse index decreases from 7.27 to 4.15%. Also, the collapse index for samples stabilized with colloidal silica decreases with increasing the relative compaction. In such a way that in samples stabilized with concentrations of 3, 4, 7 and 10% and a curing time of one day, with increasing the relative compaction from 80 to 85%, the collapse index decreases from 3.65 to 0.78%, from 2.77 to 0.26%, from 1.74 to 0.12% and from 1.36 to 0.03%, respectively (refer to Fig. 3 ). It should be noted that, as the relative compaction increases in samples stabilized with colloidal silica, the collapse potential decreases from moderate to negligible and non-collapsible. Based on the results obtained from the tests of collapse index under a stress of 400 kPa, which are shown in Table 2 , it is observed that with an increase in the relative compaction from 80 to 85%, the collapse index of unstabilized samples decreases from 8.87 to 5.33%. Also, the collapse index of stabilized samples with concentrations of 3,5,7 and 10% by dry weight and a curing time of one day decreases from 5.04 to 2.01, 3.32 to 1.23, 2.34 to 0.99 and from 0.52 to 0.04%, respectively (refer to Fig. 4 ). Therefore, with an increase in the relative compaction in all samples, collapse index decreases. Because as the relative compaction increases, the soil void ratio decreases and as a result, the collapse caused by soil wetting decreases. A similar trend about the decrease of collapse potential of samples stabilized with a certain concentration of potassium chloride was reported by Noorzad and Pakniat ( 2016 ). 3.1.2. Effect of inundation stress on the collapsibility In the collapse potential test, the stress level applied to the sample during inundation is termed \"inundation stress.\" As shown in Tables 2 through 6 , an increase in stress levels from 100 kPa to 200 kPa and subsequently to 400 kPa correlates with a rise in collapse potential. Specifically, in unstabilized samples with a relative compaction of 80%, the collapse potential increases from 4.39% at 100 kPa to 7.27% at 200 kPa, and further to 8.87% at 400 kPa. Table 3 Test results of collapse index and potential for samples stabilized with 3% colloidal silica concentration Relative compaction (%) Inundation stress (kPa) Curing time (day) Initial moisture content (%) Collapse index (%) Collapse potential 80 100 1 15.31 1.41 Negligible 200 1 15.23 3.65 Medium 7 15.17 2.24 Medium 14 15.22 1.69 Negligible 400 1 15.11 5.04 Medium 7 15.17 4.25 Medium 14 14.97 4.02 Medium 28 15.45 3.74 Medium 85 200 1 15.12 0.78 Negligible 400 1 14.91 2.01 Negligible Table 4 Test results of collapse index and potential for samples stabilized with 5% colloidal silica concentration Relative compaction (%) Inundation stress (kPa) Curing time (day) Initial moisture content (%) Collapse index (%) Collapse potential 80 100 1 15.37 0.46 Negligible 200 1 15.43 2.77 Medium 7 15.01 1.25 Negligible 400 1 15.02 3.32 Medium 7 15.20 1.93 Negligible 14 15.18 1.78 Negligible 85 200 1 15.13 0.26 Negligible 400 1 15.34 1.23 Negligible Table 5 Test results of collapse index and potential for samples stabilized with 7% colloidal silica concentration Relative compaction (%) Inundation stress (kPa) Curing time (day) Initial moisture content (%) Collapse index (%) Collapse potential 80 100 1 14.99 0.12 Negligible 200 1 14.84 1.74 Negligible 7 15.26 0.89 Negligible 400 1 15.41 2.34 Medium 7 15.25 1.22 Negligible 14 15.03 0.97 Negligible 85 200 1 15.11 0.12 Negligible 400 1 15.14 0.99 Negligible Table 6. Test results of collapse index and potential for samples stabilized with 10% colloidal silica concentration Collapse potential Collapse index (%) Initial moisture content (%) Curing time (day) Inundation stress (kPa) Relative compaction (%) Non collapsible 0.08 15.23 1 100 80 Negligible 1.36 14.85 1 200 Negligible 0.77 15.28 7 Negligible 2.04 15.17 1 400 Negligible 1.05 15.42 7 Negligible 0.71 14.92 14 Non collapsible 0.03 15.11 1 200 85 Negligible 0.52 15.39 1 400 As illustrated in Fig. 5 , for a relative compaction of 80% and a curing time of one day, an increase in the stress level from 100 kPa to 200 kPa and subsequently to 400 kPa leads to a corresponding rise in soil collapse for various concentrations of CS. Specifically, the collapse potential increases as follows: with 3% CS, from 1.45 to 3.65 and then to 5.04%; with 5% CS, from 0.46 to 2.77 and then to 3.32%; with 7% CS, from 0.12 to 1.74and then to 2.34%; and with 10% CS, from 0.08 to 1.36 and then to 2.04%. For a relative compaction of 80% and a curing time of 7 days, it is observed that with an increase in the stress level from 200 to 400 kPa, the soil collapse for concentrations of 3, 5, 7 and 10% CS, increases from 2.24 to 4.25%, from 1.25 to 1.93%, from 0.89 to 1.22% and from 0.77 to 1.05%, respectively (see Fig. 6 ). Al-Juari ( 2009 ) conducted a study on undisturbed samples with a dry unit weight of 14.91 kN/m³ and found that soil collapse is positively correlated with increasing levels of inundation stress. Also, Haeri et al ( 2012 ), reported same results for the remolded loessal soil samples. 3.1.3. Effect of curing time on the collapsibility As can be seen from Tables 2 – 6 , in general, the collapse index and collapse potential of the studied soil decrease with increasing curing time. Tests conducted on samples made with 80% density under 100 kPa stress show that the collapse potential is reduced to an acceptable level after a one-day curing time. Also, in samples made with a relative compaction of 85%, the collapse index and potential under 400 kPa stress and one-day curing time also decrease to a negligible degree of collapsibility. For this reason, the effect of curing time is omitted for these two cases. As can be seen in Fig. 7 , the collapse index for samples made with a relative compaction of 80% and 3% concentration decreases from 3.65 to 2.24 and 1.69%, respectively, with an increase in curing time from one to 7 and 14 days. Also, for concentrations of 5, 7 and 10%, with an increase in curing time from one to 7 days, the collapse index decreases from 2.77 to 1.25%, from 1.74 to 0.89% and from 1.36 to 0.77%, respectively. The results of the collapse potential tests conducted under a stress of 400 kPa, as depicted in Fig. 8 , reveal that for samples with a relative compaction of 80% and 3% colloidal silica concentration, the collapse potential decreases progressively with increasing curing time. Specifically, the collapse potential reduces from 5.04 at one day to 4.25 at 7 days, 4.02 at 14 days, and further to 3.74% at 28 days. Similarly, for higher concentrations of colloidal silica (5, 7, and 10%), the collapse potential also decreases significantly with extended curing time. For a 5% concentration, the collapse potential declines from 2.32 at one day to 1.93 at 7 days and 1.78% at 14 days. For a 7% concentration, it decreases from 2.34at one day to 1.22 at 7 days and 0.97% at 14 days. Finally, for a 10% concentration, the collapse potential drops from 2.04 at one day to 1.05 at 7 days and 0.71% at 14 days. The reason for this is that as the curing time increases, the formed gel turns into a solid and the bond between soil particles becomes stronger. Further explanations on this subject are provided in section 3.3 . 3.1.4. Effect of CS concentration on the collapsibility The colloidal silica concentration is the weight ratio of nano-silica particles to colloidal silica solution. In general, based on Tables 2 – 6 , as the colloidal silica concentration increases, the collapse index and potential decrease. The reason for this is that as the colloidal silica concentration increases, the formed gel becomes stiffer. Although it is not possible to form a hard gel from a colloidal silica solution with a concentration of 3% [7], studies were nevertheless conducted with this concentration to evaluate the effect of low concentrations of colloidal silica on the behavior of collapsible soil. The results showed that in samples made with a relative compaction of 80%, 3% concentration and one day curing time, the collapse potential under 100 kPa stress resulted in a negligible collapse degree. It was also observed in samples made with a relative compaction of 80%, 3% concentration under 200 kPa stress that with increasing curing time from one to 14 days, the collapse index reached a negligible collapse degree (Fig. 9 ). For samples made with a relative compaction of 80%, the collapse potential under a stress of 400 kPa reaches a moderate degree of collapsibility by a curing time of 14 days, but the collapse in this case is more than the permissible limit. For this reason, the collapse potential of the sample stabilized with a concentration of 3% and a curing time of 28 days is also examined. As shown in Fig. 10 , with an increase in the curing time to 28 days, the collapse potential reaches 3.73%. This value is also more than the permissible limit. Upon increasing the colloidal silica concentration to 5%, it was observed that the collapse potential under a stress of 100 kPa reached 0.46% after one day of curing. Furthermore, the collapse index increased to 1.25% after 7 days of curing. Similarly, under a stress of 400 kPa, the collapse potential was found to be 1.93% after 7 days of curing. Based on the findings of this study, the optimal concentration of stabilizer required to mitigate collapsibility is determined to be 5%. For concentrations exceeding 5%, both the collapse index and collapse potential were observed to decrease to acceptable levels as curing time increased. In a study conducted by Wong et al. ( 2018 ), it was reported that the settlement of kaolinite clay stabilized with colloidal silica is significantly lower compared to that of unstabilized kaolinite clay. Therefore, it can be concluded that, in addition to filling the soil's void spaces with colloidal silica, an increase in the concentration of colloidal silica results in the formation of a stiffer gel. Over time, the gel produced from the colloidal silica solution undergoes further solidification, transforming into a more rigid structure. Consequently, the collapsibility of soil stabilized with colloidal silica is significantly reduced. 3.2. Results of UCS tests The results of the unconfined compressive strength (UCS) tests are presented and analyzed hereunder. The investigation focuses on the influence of key parameters, including colloidal silica concentration and curing time, on the observed outcomes. 3.2.1. Effect of colloidal silica concentration on the UCS As illustrated in Fig. 11 , the addition of colloidal silica to the soil leads to an increase in the unconfined compressive strength (UCS). This improvement can be attributed to the ability of colloidal silica to fill the void spaces within the soil matrix and effectively bind the soil particles together. Furthermore, the results demonstrate that, at a constant curing time, the UCS of the samples increases with higher concentrations of colloidal silica. The primary mechanism underlying this enhancement is the increased stiffness of the gel formed as the concentration of colloidal silica rises, which contributes to the overall strengthening of the soil structure. Similar results were reported for sandy soil by Persoff et al. ( 1999 ). Another observation that can be drawn from Fig. 11 is that, at a curing time of 14 days, the strength of the sample stabilized with a 7% colloidal silica concentration achieved approximately 84% of the strength exhibited by the sample stabilized with a 10% concentration. Based on these results, it can be concluded that the optimal colloidal silica concentration, as determined through the unconfined compression test, is 7%. 3.2.2. Effect of curing time on the UCS As depicted in Fig. 12 , the UCS of samples stabilized with colloidal silica increases with prolonged curing time. For instance, at a colloidal silica concentration of 7%, the UCS increases by approximately 19% when the curing time is extended to 7 days. Similarly, an additional increase of about 20% is observed when the curing time is further extended from 7 to 14 days, and a subsequent increase of approximately 16% occurs when the curing time is extended from 14 to 28 days. This progressive enhancement in UCS can be attributed to the gradual transformation of the colloidal silica gel into a solid body over time, which contributes to the strengthening of the soil matrix. As observed, the samples stabilized with colloidal silica attain the majority of their strength by the 14-day curing time, with the rate of strength increase diminishing thereafter. Given that the initial setting time for the colloidal silica solution is approximately two hours, it can be inferred that the optimal curing time for achieving robust mechanical performance is 14 days, which corresponds to 168 times the gelation time. When clay is left undisturbed after being remolded, without any change in its moisture content, it has the potential to recover its lost strength over time. This phenomenon is referred to as thixotropy. However, as illustrated in Fig. 12 , the increase in strength over time in untreated samples is minimal. This can be attributed to the fact that the soil under investigation in this study is kaolinite clay, which exhibits very limited thixotropic behavior. Previous research on the thixotropic properties of clay minerals, including kaolinite, illite, and montmorillonite, has demonstrated that kaolinite displays almost negligible thixotropic characteristics (Skempton and Nothey, 1952). 3.2.3. Effect of colloidal silica on the stress-strain curve of soil and its brittleness To evaluate the effect of colloidal silica on the behavior of soil at the Golestan Dam construction site, this material was added to the soil at concentrations of 3, 5, 7, and 10%. The samples were prepared at the optimum moisture content and subjected to curing times of one, 7, 14, and 28 days. Subsequently, unconfined compression tests were conducted on the treated samples. Figures 13 a to d, illustrate the stress-strain curves of the stabilized soil, showcasing the effects of varying colloidal silica concentrations across different curing times. As illustrated in Figs. 13 a to d, the UCS increases significantly with an increase in colloidal silica concentration. Furthermore, for a given concentration of colloidal silica, the UCS is observed to increase progressively with curing time. Additionally, as depicted in Fig. 13 , the peak of UCS of the stabilized soil occurs at a slightly lower strain in all specimens compared to the untreated soil. Therefore, it can be concluded that this treatment enhances both the stiffness and UCS of the soil without inducing significant brittle behavior. The brittleness index is defined as the normalized difference between the maximum and residual strength, calculated by dividing this difference by the maximum strength (Eq. 2 ) (Ta'negonbadi and Noorzad, 2017 ). This dimensionless index ranges from zero to one, where a value of zero signifies complete flexibility or non-brittleness of the sample, while a value of one indicates complete brittleness. Furthermore, this index serves as an indicator of soil contractiveness and the intensity of strain softening behavior: $$\\:{I}_{B}=({q}_{p}-{q}_{r})/{q}_{p}$$ 2 where q p ​ and q r ​ represent the peak and residual strengths, respectively, as determined from the unconfined compression test. A comparative analysis was conducted between untreated and colloidal silica (CS)-treated soil samples. The brittleness indices of these samples were calculated and summarized in Table 7 . It was observed that the CS treatment did not result in a significant change in the brittleness index. Figure 14 illustrates the failure mode of both the unstabilized sample and the sample stabilized with 7% colloidal silica. Immediately after reaching the maximum strength, a shear band forms, followed by a sudden loss of strength, indicative of brittle failure. As observed, the failure angle in both the unstabilized and stabilized samples is similar, approximating 45 degrees. Table 7 Results of the unconfined compression test and brittleness index for untreated and treated samples at various curing times Sample code Colloidal silica concentration (%) Curing time (day) Peak strength (kP) Residual strength (kPa) Brittleness index CL-0-1 0 1 122.29 26.04 0.79 CL-3-1 3 194.99 31.70 0.84 CL-5-1 5 230.22 38.98 0.83 CL-7-1 7 272.77 40.86 0.85 CL-10-1 10 352.52 52.82 0.85 CL-0-7 0 7 128.47 23.44 0.82 CL-3-7 3 213.25 34.39 0.84 CL-5-7 5 291.45 45.87 0.84 CL-7-7 7 325.47 45.12 0.86 CL-10-7 10 412.12 56.77 0.86 CL-0-14 0 14 131.58 22.22 0.83 CL-3-14 3 265.17 42.15 0.84 CL-5-14 5 340.07 46.67 0.86 CL-7-14 7 390.63 50.48 0.87 CL-10-14 10 464.54 56.26 0.88 CL-0-28 0 28 148.15 23.44 0.84 CL-3-28 3 297.93 42.16 0.86 CL-5-28 5 413.35 43.26 0.90 CL-7-28 7 452.38 55.01 0.88 CL-10-28 10 504.97 77.73 0.85 However, the unconfined compression test revealed that as the CS concentration increased from 0 to 10%, the peak axial stress increased from 122 kPa to 505 kPa, corresponding to a maximum increment of up to 314%. These findings underscore the effectiveness of CS stabilization in enhancing the mechanical properties of this soil. 3.2.4. Effect of colloidal silica on the secant modulus of deformation and absorbed energy The secant modulus of deformation (E 50 ) in the unconfined compression test is determined by calculating the slope of the line in the stress-strain curve. Specifically, the point corresponding to 50% of the peak strength is identified and connected to the origin of the coordinate system. The strain corresponding to this point is then calculated, and the resulting slope of the line provides the value of the secant modulus (E 50 ). Figure 15 illustrates the variations in the secant modulus (E 50 ) as a function of colloidal silica concentration at different curing times. From this figure, it is evident that the secant modulus increases significantly with prolonged curing time. For instance, in the case of a sample stabilized with a 5% colloidal silica concentration, the E 50 value is observed to increase by approximately 48% when the curing time is extended from one to 28 days. This phenomenon can be attributed to the transformation of the colloidal silica gel into a solid phase over time. Consequently, both the strength of the material and the associated secant modulus are enhanced. Absorbed energy represents the amount of energy required to deform a material. In an unconfined compression test, the absorbed energy is determined by calculating the area under the stress-strain curve at a specified strain (e.g., 15%). Figure 16 presents the graph of absorbed energy as a function of curing time for various concentrations of colloidal silica. As observed, at a constant curing time, the absorbed energy increases with higher concentrations of colloidal silica. Additionally, for a given concentration, the absorbed energy rises as the curing time is extended. This increase in absorbed energy can be attributed to the enhancement in soil strength, which, in turn, leads to an expansion in the area under the stress-strain curve. 3.3. Effect on microstructure The SEM micrographs were utilized to gain a deeper understanding of the effects of colloidal silica (CS) and to analyze the microstructural characteristics of both untreated and CS-treated soils. Figure 17 present scanning electron microscope (SEM) images of both unstabilized and colloidal silica-stabilized soil samples, captured at a magnification of 500x. As previously discussed, collapsible soils exhibit an open and semi-stable structure, which accounts for the visible voids between soil particles in the unstabilized sample. These voids are highlighted by red circles in the corresponding images. In contrast, the SEM image of the stabilized sample reveals that the colloidal silica gel effectively fills the interstitial spaces between soil particles, promoting inter-particle bonding and enhancing the overall structural integrity. By stabilization of the soil, its structure undergoes significant changes as a result of the chemical reactions between the soil and the colloidal silica mixture, which lead to the formation of gel. A comparison of Figs. 17 a,b highlights a substantial transformation in the soil's structure. It is evident that the untreated soil, which initially exhibits a grain-based structure in Fig. 17 a, transitions to a more aggregated form in Fig. 17 b. This change can be attributed to the chemical reactions and the production of colloidal silica gel, which alter the soil's structure. 4. Conclusion In this reaearch, colloidal silica effect on the stabilization of collapsible soil was investigated. The most important results of the tests can be summarized as following cases: The addition of colloidal silica to the collapsible soil investigated in this study resulted in a reduction in both the collapse index and collapse potential. This improvement can be attributed to the gel formed from the colloidal silica solution, which effectively fills the voids between soil particles, thereby reducing soil compressibility. The optimal concentration for mitigating soil collapsibility was found to be 5%, as it successfully reduced the collapse potential from severe to negligible levels. The results of the collapsibility tests indicated that as the relative compaction increased from 80 to 85%, both the collapse potential and collapse index of the unstabilized and CS-stabilized samples decreased. One of the key factors influencing the collapsibility of stabilized soil is the curing time. Research has demonstrated that as the curing time increases, both the collapse index and collapse potential decrease. This reduction can be attributed to the gradual transformation of the gel formed by the colloidal silica solution into a solid state over time. The test results demonstrated that soil collapsibility increases with rising inundation stress levels, specifically from 100 kPa to 200 kPa and further to 400 kPa. Consequently, it can be inferred that an increase in the inundation stress level is associated with a corresponding intensification of soil collapsibility. The addition of colloidal silica to the soil resulted in an increase in its unconfined compressive strength (UCS); however, no significant change was observed in the failure strain. The UCS was found to increase with higher concentrations of colloidal silica, as the gel formed becomes progressively stiffer. At a curing time of 14 days, the strength of the sample stabilized with a 7% colloidal silica concentration reached approximately 84% of the strength of the sample stabilized with a 10% concentration. Based on these findings, it can be concluded that the optimal colloidal silica concentration, as determined by the unconfined compression test, is 7%. Based on the stress-strain curves of UCS tests, it is observed that this stabilization increases both the stiffness and UCS of the soil without leading to a considerable brittle behavior. In general, as the curing time increases from 1 to 28 days, the unconfined compressive strength (UCS) of the samples also increases. However, the rate of strength gain diminishes after a curing period of 14 days. Consequently, the optimal curing age for achieving maximum strength in the stabilized samples is 14 days. The observed increase in strength in samples stabilized with colloidal silica can be attributed to the progressive solidification of the colloidal silica gel over time. The SEM image of the unstabilized soil demonstrates that the collapsible soil structure is open and semi-stable, characterized by visible voids between soil particles. In contrast, the SEM micrograph of the treated soil indicates that the colloidal silica gel successfully fills the interstitial spaces between soil particles. This filling effect promotes inter-particle bonding, thereby significantly enhancing the overall structural integrity of the soil. Declarations Funding The research presented in this paper was financially supported by Babol Noshirvani University of Technology through grant program of BNUT/370723/03. Author Contribution The authors contributed to this work as follows:Fatemeh Bakhshandeh : Conceptualization, Methodology, Investigation, Writing – Original Draft Preparation.Reza Noorzad : Supervision, Conceptualization, Methodology, Validation, Review & Editing.Bahram Ta'negonbadi : Conceptualization, Writing – Review & Editing.All authors have read and approved the final version of the manuscript and agree to be accountable for all aspects of the work. Data Availability All data generated or analyzed during this study are included in the paper. Additional Information The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References Al-Juari, K.A., 2009. Volume change measurement of collapsible soil stabilized with lime and waste lime. Tikrit Journal of Engineering Sciences, 16(3), pp.38-54. Al-Obaidi, Q.A., Ibrahim, S.F. and Schanz, T., 2013. 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Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort (12,400 ft-lbf/ft3 (600 kN-m/m3)). Annual Book of ASTM Standards, USA. ASTM D-7928, 2017. Standard Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis. Annual Book of ASTM Standards, USA. ASTM D-854, 2014. Standard Test Methods for Specific Gravity of Soil Solids by Water Pycnometer. Annual Book of ASTM Standards, USA. Bolisetti, T., Reitsma, S. and Balachandar, R., 2009. Experimental investigations of colloidal silica grouting in porous media. Journal of geotechnical and geoenvironmental engineering, 135(5), pp.697-700. Cerato, A.B., Miller, G.A. and Hajjat, J.A., 2009. Influence of clod-size and structure on wetting-induced volume change of compacted soil. Journal of geotechnical and geoenvironmental engineering, 135(11), pp.1620-1628. Fang, H.Y., 2013. Foundation engineering handbook. Springer Science & Business Media. Gallagher, P.M., Pamuk, A. and Abdoun, T., 2007. Stabilization of liquefiable soils using colloidal silica grout. Journal of Materials in Civil Engineering, 19(1), pp.33-40. Georgiannou, V.N., Pavlopoulou, E.M. and Bikos, Z., 2017. Mechanical behaviour of sand stabilised with colloidal silica. Geotechnical Research, 4(1), pp.1-11. Haeri, S.M., Zamani, A. and Garakani, A.A., 2012. Collapse potential and permeability of undisturbed and remolded loessial soil samples. In Unsaturated Soils: Research and Applications: Volume 1 (pp. 301-308). Springer Berlin Heidelberg. Houston, S.L., Houston, W.N. and Mahmoud, H.H., 1995. Interpretation and comparison of collapse measurement techniques. In Genesis and properties of collapsible soils (pp. 217-224). Dordrecht: Springer Netherlands. Houston, S.L., Houston, W.N., Zapata, C.E. and Lawrence, C., 2001. Geotechnical engineering practice for collapsible soils. Geotechnical & Geological Engineering, 19, pp.333-355. Kakavand, A. and Dabiri, R., 2018. Experimental study of applying colloidal nano Silica in improving sand-silt mixtures. International Journal of Nano Dimension, 9(4), pp.357-373. Krishnan, J., Sharma, P. and Shukla, S., 2021. Experimental investigations on the mechanical properties of sand stabilized with colloidal silica. Iranian Journal of Science and Technology, Transactions of Civil Engineering, 45, pp.1737-1758. Lin, Y., 2006. Colloidal silica transport mechanisms for passive site stabilization of liquefiable soils. Drexel University. Mahmood, M.S. and Abrahim, M.J., 2021, February. A review of collapsible soils behavior and prediction. In IOP Conference Series: Materials Science and Engineering (Vol. 1094, No. 1, p. 012044). IOP Publishing. Noorzad, R. and Nouri Delavar, I., 2019. Investigation into the short-term behavior of silty sand stabilized with colloidal silica. Scientia Iranica, 26(3), pp.1206-1213. Noorzad, R. and Pakniat, H., 2016. Investigating the effect of sample disturbance, compaction and stabilization on the collapse index of soils. Environmental Earth Sciences, 75, pp.1-9. Pedrotti, M., Wong, C., El Mountassir, G., Renshaw, J.C. and Lunn, R.J., 2020. Desiccation behaviour of colloidal silica grouted sand: A new material for the creation of near surface hydraulic barriers. Engineering Geology, 270, p.105579. Persoff, P., Apps, J., Moridis, G. and Whang, J.M., 1999. Effect of dilution and contaminants on sand grouted with colloidal silica. Journal of geotechnical and geoenvironmental engineering, 125(6), pp.461-469. Rollins, K.M. and Kim, J., 2010. Dynamic compaction of collapsible soils based on US case histories. Journal of geotechnical and geoenvironmental engineering, 136(9), pp.1178-1186. Seif, M.E., MolaAbasi, H., Saba, H. and Mirhosseini, S.M., 2024. Investigating the impact of nano-colloidal silica on sandy clay strength: Experimental results and stress-strain modeling insights. Construction and Building Materials, 438, p.137105. Skempton, A.W. and Northey, R.D., 1952. The sensitivity of clays. Geotechnique, 3(1), pp.30-53. Ta'negonbadi, B. and Noorzad, R., 2017. Stabilization of clayey soil using lignosulfonate. Transportation Geotechnics, 12, pp.45-55. Wong, C., Pedrotti, M., El Mountassir, G. and Lunn, R.J., 2018. A study on the mechanical interaction between soil and colloidal silica gel for ground improvement. Engineering geology, 243, pp.84-100. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 16 Aug, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 12 Jun, 2025 Reviews received at journal 12 Jun, 2025 Reviews received at journal 03 Jun, 2025 Reviewers agreed at journal 28 May, 2025 Reviewers agreed at journal 28 May, 2025 Reviewers invited by journal 28 May, 2025 Editor assigned by journal 28 May, 2025 Editor invited by journal 28 May, 2025 Submission checks completed at journal 28 May, 2025 First submitted to journal 13 May, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-6655792\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":463512768,\"identity\":\"1be490e2-ff39-4949-9f6d-5cbdbac3b6af\",\"order_by\":0,\"name\":\"Fatemeh Bakhshandeh\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Babol Noshirvani University of Technology\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Fatemeh\",\"middleName\":\"\",\"lastName\":\"Bakhshandeh\",\"suffix\":\"\"},{\"id\":463512769,\"identity\":\"f14340ce-fba4-48a1-9379-e68851a0b949\",\"order_by\":1,\"name\":\"Reza 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12\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":36189,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eVariation of unconfined compressive strength as a function of curing time for various colloidal silica concentration\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"image12.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6655792/v1/5c6184b5e12023f30a5f73bf.png\"},{\"id\":83664092,\"identity\":\"9e045a31-ceca-4782-9f17-d4c21be07640\",\"added_by\":\"auto\",\"created_at\":\"2025-05-30 10:55:58\",\"extension\":\"png\",\"order_by\":13,\"title\":\"Figure 13\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":105063,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eStress-strain curves of soil stabilized with various concentrations of colloidal silica after: a) 1, b) 7, c) 14 and d) 28 days of curing\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"image13.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6655792/v1/9447b9efa3518e3bf4500c9f.png\"},{\"id\":83664100,\"identity\":\"357bd105-4bcf-48ec-b48b-1d3f5f2b04f4\",\"added_by\":\"auto\",\"created_at\":\"2025-05-30 10:55:58\",\"extension\":\"png\",\"order_by\":14,\"title\":\"Figure 14\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":62642,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eFailure mode of the samples: a) unstabilized and b) stabilized with 7% colloidal silica concentration, at 14-day curing time\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"image14.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6655792/v1/c12f70d5faa9171f75aeb057.png\"},{\"id\":83664108,\"identity\":\"c8b3c4d8-24c1-4667-82d9-57efd36381b6\",\"added_by\":\"auto\",\"created_at\":\"2025-05-30 10:55:58\",\"extension\":\"png\",\"order_by\":15,\"title\":\"Figure 15\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":80208,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eSecant modulus as a function of colloidal silica concentration for different curing times\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"image15.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6655792/v1/b72a6e290cae67c4e0290d79.png\"},{\"id\":83664093,\"identity\":\"daee7986-e1ed-4014-9f32-5a929a52d598\",\"added_by\":\"auto\",\"created_at\":\"2025-05-30 10:55:58\",\"extension\":\"png\",\"order_by\":16,\"title\":\"Figure 16\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":117249,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eAbsorbed energy versus curing time for different concentrations of colloidal silica\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"image16.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6655792/v1/6333be09d9e3745748746a94.png\"},{\"id\":83664096,\"identity\":\"e3ca0917-532b-47e0-8d11-13747ea5d5d9\",\"added_by\":\"auto\",\"created_at\":\"2025-05-30 10:55:58\",\"extension\":\"png\",\"order_by\":17,\"title\":\"Figure 17\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":81953,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eSEM micrograph of a) unstabilized and b) stabilized sample\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"image17.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6655792/v1/980cdbd49dd9497a7b7d0627.png\"},{\"id\":89310575,\"identity\":\"4a53c6db-29ce-4f41-bb4d-55f6054736c6\",\"added_by\":\"auto\",\"created_at\":\"2025-08-18 16:08:21\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":2228905,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6655792/v1/fa31388b-ff1c-443c-8b49-21633a593411.pdf\"}],\"financialInterests\":\"No competing interests reported.\",\"formattedTitle\":\"Experimental Investigation of the Properties of Collapsible Soil Stabilized by Colloidal Silica\",\"fulltext\":[{\"header\":\"1. Introduction\",\"content\":\"\\u003cp\\u003eSeveral factors, including rainfall, rising groundwater levels, and human activities such as washing and irrigation, contribute to an increase in soil moisture content (Mahmood and Abrahim, \\u003cspan citationid=\\\"CR22\\\" class=\\\"CitationRef\\\"\\u003e2021\\u003c/span\\u003e). The partial or complete wetting of moisture-sensitive soils results in either collapse or swelling. Consequently, an increase in soil moisture content can lead to volume changes, thereby reducing both bearing capacity and shear strength. As a result, this issue presents a significant challenge in the design of foundations, both during and after the construction of engineering structures (Al-Obaidi et al., \\u003cspan citationid=\\\"CR2\\\" class=\\\"CitationRef\\\"\\u003e2013\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eCollapsible soil is characterized as unsaturated soil that can endure relatively high pressures without exhibiting significant changes in volume; however, it is susceptible to abrupt and substantial volume loss upon an increase in moisture content (Cerato et al., \\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e2009\\u003c/span\\u003e). Collapsible soil is, in fact, a moisture-sensitive soil that undergoes a reduction in volume as moisture content increases. If such soil is not treated prior to construction, subsidence resulting from soil collapse can lead to significant financial costs (Houston et al., \\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e2001\\u003c/span\\u003e; Rollins and Kim, \\u003cspan citationid=\\\"CR27\\\" class=\\\"CitationRef\\\"\\u003e2010\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eSeveral methods have been proposed to minimize or eliminate soil collapsibility. The selection of the most suitable method depends on factors such as the depth of the collapsible soil, the type of structure, its cost, and the feasibility of the method (Houston et al., \\u003cspan citationid=\\\"CR17\\\" class=\\\"CitationRef\\\"\\u003e1995\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eChemical stabilization is one of the oldest and most widely used methods for soil improvement, typically involving the mixing of soil with one or more types of additives. Various materials, including lime, cement, silicates, resins, and acids, have been employed to stabilize soil (Fang, \\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e2013\\u003c/span\\u003e). Sodium silicate has been utilized as a chemical slurry for injection into the soil; however, colloidal silica presents a suitable alternative due to its low viscosity (Bolisetti et al., \\u003cspan citationid=\\\"CR11\\\" class=\\\"CitationRef\\\"\\u003e2009\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eColloidal silica is a solution that undergoes gelation when sodium chloride is added or its acidity is altered. Consequently, it can be injected into the soil or mixed with it, ultimately filling the voids within the soil upon gelation (Persoff et al., \\u003cspan citationid=\\\"CR26\\\" class=\\\"CitationRef\\\"\\u003e1999\\u003c/span\\u003e; Lin, \\u003cspan citationid=\\\"CR21\\\" class=\\\"CitationRef\\\"\\u003e2006\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003ePermeation grouting involves injecting a low-viscosity slurry to fill voids within the soil. Cement grouts, due to their high initial viscosity and large particle size, require high injection pressures to permeate the soil. In contrast, chemical grouts are easier to inject due to their lower initial viscosity compared to cement grouts; however, they are often more expensive and may contain toxic compounds. Colloidal silica, on the other hand, offers the advantage of a low viscosity (similar to water) and very fine particles, while also being chemically non-toxic (Pedrotti et al., \\u003cspan citationid=\\\"CR25\\\" class=\\\"CitationRef\\\"\\u003e2020\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eNowadays, colloidal silica, as a preferable soil stabilizer increasingly used (Georgiannou et al., \\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e2017\\u003c/span\\u003e; Kakavand and Dabiri, \\u003cspan citationid=\\\"CR19\\\" class=\\\"CitationRef\\\"\\u003e2018\\u003c/span\\u003e; Wong et al., \\u003cspan citationid=\\\"CR31\\\" class=\\\"CitationRef\\\"\\u003e2018\\u003c/span\\u003e; Noorzad and Nouri Delavar, \\u003cspan citationid=\\\"CR23\\\" class=\\\"CitationRef\\\"\\u003e2019\\u003c/span\\u003e; Krishnan et al., \\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e2021\\u003c/span\\u003e; Seif et al., \\u003cspan citationid=\\\"CR28\\\" class=\\\"CitationRef\\\"\\u003e2024\\u003c/span\\u003e). The colloidal silica (CS) lead to decrease collapsibility and increase strength and durability of the soil. Additionally, its use does not harm the environment (Krishnan et al., \\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e2021\\u003c/span\\u003e). The useful life of colloidal silica exceeds 25 years, whereas the useful lives of sodium silicate and acrylic grout range from approximately 10 to 20 years. The cost of colloidal silica at a concentration of 5% by weight is estimated to be comparable to that of microfine cement. Furthermore, the expenses associated with colloidal silica injection are significantly lower than those related to cement injection (Gallagher et al., \\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e2007\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eWong et al. (\\u003cspan citationid=\\\"CR31\\\" class=\\\"CitationRef\\\"\\u003e2018\\u003c/span\\u003e) conducted a series of one-dimensional consolidation and shear strength tests to investigate the behavior of sand and kaolinite clay stabilized with colloidal silica. Their findings indicated that the addition of colloidal silica significantly enhances the stiffness and peak friction angle of the sand. Furthermore, the consolidation tests revealed that the stabilized clay exhibited a lower void ratio compared to the unstabilized samples during the initial stages of testing. Additionally, it was observed that the settlement rate of the stabilized clay remained low under vertical stresses below 30 kPa; however, as vertical stress increased, the settlement rates for both the stabilized and unstabilized samples converged. Krishnan et al. (\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e2021\\u003c/span\\u003e) investigated the static and dynamic behavior of colloidal silica-stabilized sand. The findings from their study indicated that the optimal concentration of colloidal silica for relative densities of 30%, 40%, and 60% is 12.5%, 11%, and 10%, respectively. The increased cohesion in colloidal silica-stabilized sand was attributed primarily to the specific surface area of the colloidal silica particles and the formation of siloxane bonds. Additionally, the results from dynamic experiments demonstrated that the application of colloidal silica at the optimal concentration effectively reduces the tendency for liquefaction.\\u003c/p\\u003e \\u003cp\\u003eMost of the past studies performed on the CS treated soil, have mainly focused on the sand, silty sand and sandy clay (Georgiannou et al., \\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e2017\\u003c/span\\u003e; Kakavand and Dabiri, \\u003cspan citationid=\\\"CR19\\\" class=\\\"CitationRef\\\"\\u003e2018\\u003c/span\\u003e; Noorzad and Nouri Delavar, \\u003cspan citationid=\\\"CR23\\\" class=\\\"CitationRef\\\"\\u003e2019\\u003c/span\\u003e; Krishnan et al., \\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e2021\\u003c/span\\u003e; Seif et al., \\u003cspan citationid=\\\"CR28\\\" class=\\\"CitationRef\\\"\\u003e2024\\u003c/span\\u003e). Few studies have been performed on clay (Wong et al., \\u003cspan citationid=\\\"CR31\\\" class=\\\"CitationRef\\\"\\u003e2018\\u003c/span\\u003e). Furthermore, no research has been conducted to examine the collapsibility and strength characteristics of colloidal silica-stabilized collapsible soils, specifically loess soils (CL). The main purpose of this research, was to evaluate the influence of various contents of CS on the collapsibility, compaction properties and unconfined compressive strength (UCS) of loess soils. Also, the effect of relative compaction and aging on the collapsibility and strength properties of CS-treated and untreated collapsible soil was investigated. Additionally, the findings of this study were enhanced by conducting a microstructural analysis of the base soil both prior to and following stabilization, utilizing a scanning electron microscope (SEM).\\u003c/p\\u003e\"},{\"header\":\"2. Experimental investigation\",\"content\":\"\\u003cdiv id=\\\"Sec3\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e2.1. Materials\\u003c/h2\\u003e \\u003cdiv id=\\\"Sec4\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e2.1.1. Clay (CL)\\u003c/h2\\u003e \\u003cp\\u003eConsidering the prevalence of collapsible soils in Golestan Province, the soil utilized in this study was sourced from the construction site of the Golestan Dam, situated 12 kilometers northeast of Gonbade Kavous city, Iran. Figure\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e shows the grain size distribution of the studied soil that was determined using sieve analysis and hydrometer test according to ASTM-D6913 (ASTM, 2017) and ASTM-D7928 (ASTM, 2017).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eBased on the results of the Atterberg limits tests conducted in accordance with ASTM D 4318 (ASTM, 2017), the liquid limit and plastic limit of the soil were approximately 27% and 17%, respectively. This classification identifies the soil as low plasticity clay (CL) according to ASTM D 2487 (ASTM, 2017). The compaction test, performed following ASTM D 698 (ASTM, \\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e2021\\u003c/span\\u003e), indicated that the optimum water content and maximum dry unit weight of the soil were 15.06% and 18.09 kN/m\\u0026sup3;, respectively. Furthermore, the specific gravity was measured at 2.71, determined using ASTM D 854 (ASTM, 2014).\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec5\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e2.1.2. Colloidal silica (CS)\\u003c/h2\\u003e \\u003cp\\u003eThe colloidal silica employed in this study was produced by Dr. Khan Company, India. The properties of this product are detailed in Table\\u0026nbsp;\\u003cspan refid=\\\"Tab1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e. Figure\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e illustrates the colloidal silica before and after gelation. In this study, the required volume of concentrated solution (30% by weight) to prepare more dilute solutions (3, 5, 7, and 10% by weight) was determined according to the following equation:\\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab1\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 1\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eCharacteristics of used colloidal silica in this research\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"5\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eWeight percent of silica (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eParticle size (\\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:\\\\text{N}\\\\text{a}\\\\text{n}\\\\text{o}\\\\text{m}\\\\text{e}\\\\text{t}\\\\text{e}\\\\text{r}\\\\)\\u003c/span\\u003e\\u003c/span\\u003e)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003epH\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eDensity (gr/ml)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003eViscosity (Centipoise)\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e30\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e10\\u0026ndash;14\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e8.5\\u0026ndash;10\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e1.19\\u0026ndash;1.21\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e7\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003c/table\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv id=\\\"Equ1\\\" class=\\\"Equation\\\"\\u003e \\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equ1\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:{V}_{1}=\\\\frac{{C}_{2}}{{C}_{1}}{V}_{2}$$\\u003c/div\\u003e \\u003cdiv class=\\\"EquationNumber\\\"\\u003e1\\u003c/div\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003cp\\u003eIn which, C\\u003csub\\u003e1\\u003c/sub\\u003e: Concentrated solution concentration, C\\u003csub\\u003e2\\u003c/sub\\u003e: Concentration of the desired dilute solution, V\\u003csub\\u003e1\\u003c/sub\\u003e: Required volume of concentrated solution and V\\u003csub\\u003e2\\u003c/sub\\u003e: Volume of desired dilute solution.\\u003c/p\\u003e \\u003cp\\u003eBased on the experimental results, the gelation time of the colloidal silica solution employed in this study was determined to be approximately two hours.\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec6\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e2.2. Laboratory tests\\u003c/h2\\u003e \\u003cp\\u003eLaboratory tests including collapsibility potential and UCS was performed with different percentages of CS.\\u003c/p\\u003e \\u003cp\\u003eIn order to clarify the results, SEM analysis was applied to trace the microstructural changes.\\u003c/p\\u003e \\u003cp\\u003eStabilized soil samples for this experimental research were prepared using four percentages (3, 5, 7 and 10%) of CS by soil dry weight.\\u003c/p\\u003e \\u003cdiv id=\\\"Sec7\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e2.2.1. Collapse potential test\\u003c/h2\\u003e \\u003cp\\u003eThe effect of CS on the collapsibility of stabilized soil was investigated by conducting a collapse potential test based on ASTM D 5333 (ASTM, 2017).\\u003c/p\\u003e \\u003cp\\u003eTo prepare stabilized samples, at first, the required dry soil weight is determined based on the volume of the mold (consolidation ring), the desired relative compaction and the obtained results from the standard compaction test. The quantity of colloidal silica necessary for sample preparation is determined based on the target moisture content (optimum moisture content). This process involves calculating the volume of water needed to achieve the desired moisture percentage in the soil while taking into account the concentration of the colloidal silica solution (3, 5, 7, and 10% by weight). Consequently, the amount of the colloidal silica solution with the specified concentration is computed accordingly. Concentrated colloidal silica (30% by weight) is combined with a sodium chloride solution containing the requisite water for diluting the colloidal silica solution, and the necessary sodium chloride particles, to provide a sodium chloride solution of the desired normality. Then the resulting colloidal silica solution is mixed with the required amount of dry soil. According to the research conducted by Noorzad and Pakniat (\\u003cspan citationid=\\\"CR24\\\" class=\\\"CitationRef\\\"\\u003e2016\\u003c/span\\u003e), the relative compaction of undisturbed samples obtained from the Golestan Dam construction site is 80%, therefore, the collapse potential investigation is conducted with a relative compaction of 80%. Also, to investigate the effect of relative compaction on collapse potential, samples with a relative compaction of 85% were also made.\\u003c/p\\u003e \\u003cp\\u003eImmediately after preparation of a homogenous mixture from the soil and colloidal silica solution, the resulting mixture was compacted in 3 layers using static compaction to prepare the uniform samples (50 mm diameter by 20 mm height). After compaction of any layer its surface was scarified about 3 mm to reach the fair bond. Then, the compacted specimens were sealed in a double layered plastic wrap and kept in a room with controlled temperature under various curing times. (1, 7, 14 and 28 days).\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec8\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e2.2.2. Unconfined compression test\\u003c/h2\\u003e \\u003cp\\u003eThe effect of the additive on the enhancement of shear strength in treated soil was examined through unconfined compressive testing, conducted in accordance with ASTM D 2166 (ASTM, 2024).\\u003c/p\\u003e \\u003cp\\u003eTo prepare stabilized specimens, the materials are initially mixed in a manner similar to that described in the previous section. However, it is important to note that the quantities of materials required are tailored for specimens measuring 50 mm in diameter and 100 mm in height, with a target relative compaction of 95%. The recommended compaction of fine materials used in an embankment for the majority of construction projects is between 95 and 100% of the maximum dry unit weight (MDUW) (Ta'negonbadi and Noorzad, \\u003cspan citationid=\\\"CR30\\\" class=\\\"CitationRef\\\"\\u003e2017\\u003c/span\\u003e). Consequently, a target dry unit weight of 95% MDUW was selected for the samples utilized in these tests.\\u003c/p\\u003e \\u003cp\\u003eImmediately following the preparation of a homogeneous mixed of soil and colloidal silica solution, the resulting mixture was compacted into five layers using static compaction to create uniform specimens measuring 50 mm in diameter and 100 mm in height. According to the research performed by Ta'negonbadi and Noorzad (\\u003cspan citationid=\\\"CR30\\\" class=\\\"CitationRef\\\"\\u003e2017\\u003c/span\\u003e), to assess the uniformity of the samples, several specimens were fabricated and each was subsequently cut into 6 to 8 segments using a narrow wire saw. The weight and volume of each segment were then recorded. Ultimately, the unit weight and density of each segment were calculated, revealing that the variation in density along height of the sample from the target density was negligible. Consequently, the prepared samples can be regarded as uniform. Once the initial setting time has elapsed, the sample is extracted from the mold using a jack and subsequently stored in a double layered plastic wrap until the specified curing time is reached.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec9\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e2.2.3. Analysis of microstructure\\u003c/h2\\u003e \\u003cp\\u003eScanning Electron Microscopy (SEM) analysis was conducted on both CS-stabilized and unstabilized soils. Based on the findings from the SEM analysis, the stabilization mechanisms of the stabilized specimens were examined, and the observations obtained from the tests were elucidated.\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/div\\u003e\"},{\"header\":\"3. Results and discussion\",\"content\":\"\\u003cdiv id=\\\"Sec11\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e3.1. Test results of determining the collapse potential and index\\u003c/h2\\u003e \\u003cp\\u003eThe test results for determining the collapse potential and collapse index are presented in Tables\\u0026nbsp;\\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e\\u0026ndash;\\u003cspan refid=\\\"Tab3\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003e. The parameters examined in these tests include:\\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab2\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 2\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eTest results of collapse index and potential of untreated samples\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"4\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eRelative compaction (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eInundation stress (kPa)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eCollapse index (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eCollapse potential\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\" morerows=\\\"2\\\" rowspan=\\\"3\\\"\\u003e \\u003cp\\u003e80\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e100\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e4.39\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e200\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e7.27\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eRelatively severe\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e400\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e8.87\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eRelatively severe\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\" morerows=\\\"1\\\" rowspan=\\\"2\\\"\\u003e \\u003cp\\u003e85\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e200\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e4.15\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e400\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e5.33\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003c/table\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003cul\\u003e \\u003cli\\u003e \\u003cp\\u003eFour different concentrations of colloidal silica (3, 5, 7 and 10% by weight)\\u003c/p\\u003e \\u003c/li\\u003e \\u003cli\\u003e \\u003cp\\u003eTwo relative compactions for the collapse potential test (80 and 85% of MDUW)\\u003c/p\\u003e \\u003c/li\\u003e \\u003cli\\u003e \\u003cp\\u003eFour curing times (1, 7, 14 and 28 days)\\u003c/p\\u003e \\u003c/li\\u003e \\u003c/ul\\u003e \\u003c/p\\u003e \\u003cp\\u003eThe effect of each of the above parameters on the behavior of stabilized samples is examined separately hereunder.\\u003c/p\\u003e \\u003cdiv id=\\\"Sec12\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e3.1.1. Effect of relative compaction on the collapsibility\\u003c/h2\\u003e \\u003cp\\u003eAs the results of the tests of collapse potential under a stress of 100 kPa show, at this stress level, the collapse potential for specimens stabilized with a relative compaction of 80%, decreases to an acceptable value. For this reason, the effect of relative compaction at this stress level is omitted (refer to Tables\\u0026nbsp;\\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e\\u0026ndash;\\u003cspan refid=\\\"Tab3\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003e). According to Table\\u0026nbsp;\\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e, it is observed that with increasing the relative compaction in unstabilized samples, the collapse index decreases. So that with increasing the relative compaction from 80 to 85%, the collapse index decreases from 7.27 to 4.15%.\\u003c/p\\u003e \\u003cp\\u003eAlso, the collapse index for samples stabilized with colloidal silica decreases with increasing the relative compaction. In such a way that in samples stabilized with concentrations of 3, 4, 7 and 10% and a curing time of one day, with increasing the relative compaction from 80 to 85%, the collapse index decreases from 3.65 to 0.78%, from 2.77 to 0.26%, from 1.74 to 0.12% and from 1.36 to 0.03%, respectively (refer to Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e).\\u003c/p\\u003e\\u003cp\\u003eIt should be noted that, as the relative compaction increases in samples stabilized with colloidal silica, the collapse potential decreases from moderate to negligible and non-collapsible.\\u003c/p\\u003e \\u003cp\\u003eBased on the results obtained from the tests of collapse index under a stress of 400 kPa, which are shown in Table\\u0026nbsp;\\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e, it is observed that with an increase in the relative compaction from 80 to 85%, the collapse index of unstabilized samples decreases from 8.87 to 5.33%.\\u003c/p\\u003e \\u003cp\\u003eAlso, the collapse index of stabilized samples with concentrations of 3,5,7 and 10% by dry weight and a curing time of one day decreases from 5.04 to 2.01, 3.32 to 1.23, 2.34 to 0.99 and from 0.52 to 0.04%, respectively (refer to Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003eTherefore, with an increase in the relative compaction in all samples, collapse index decreases. Because as the relative compaction increases, the soil void ratio decreases and as a result, the collapse caused by soil wetting decreases. A similar trend about the decrease of collapse potential of samples stabilized with a certain concentration of potassium chloride was reported by Noorzad and Pakniat (\\u003cspan citationid=\\\"CR24\\\" class=\\\"CitationRef\\\"\\u003e2016\\u003c/span\\u003e).\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec13\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e3.1.2. Effect of inundation stress on the collapsibility\\u003c/h2\\u003e \\u003cp\\u003eIn the collapse potential test, the stress level applied to the sample during inundation is termed \\\"inundation stress.\\\" As shown in Tables\\u0026nbsp;\\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e through \\u003cspan refid=\\\"Tab3\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003e, an increase in stress levels from 100 kPa to 200 kPa and subsequently to 400 kPa correlates with a rise in collapse potential. Specifically, in unstabilized samples with a relative compaction of 80%, the collapse potential increases from 4.39% at 100 kPa to 7.27% at 200 kPa, and further to 8.87% at 400 kPa.\\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab4\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 3\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eTest results of collapse index and potential for samples stabilized with 3% colloidal silica concentration\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"6\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c6\\\" colnum=\\\"6\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eRelative compaction (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eInundation stress (kPa)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eCuring time (day)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eInitial moisture content (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003eCollapse index (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eCollapse potential\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\" morerows=\\\"7\\\" rowspan=\\\"8\\\"\\u003e \\u003cp\\u003e80\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e100\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.31\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1.41\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\" morerows=\\\"2\\\" rowspan=\\\"3\\\"\\u003e \\u003cp\\u003e200\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.23\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e3.65\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.17\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e2.24\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e14\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.22\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1.69\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\" morerows=\\\"3\\\" rowspan=\\\"4\\\"\\u003e \\u003cp\\u003e400\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.11\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e5.04\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.17\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e4.25\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e14\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e14.97\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e4.02\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e28\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.45\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e3.74\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\" morerows=\\\"1\\\" rowspan=\\\"2\\\"\\u003e \\u003cp\\u003e85\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e200\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.12\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e0.78\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e400\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e14.91\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e2.01\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003c/table\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab5\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 4\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eTest results of collapse index and potential for samples stabilized with 5% colloidal silica concentration\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"6\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c6\\\" colnum=\\\"6\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eRelative compaction (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eInundation stress (kPa)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eCuring time (day)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eInitial moisture content (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003eCollapse index (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eCollapse potential\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\" morerows=\\\"5\\\" rowspan=\\\"6\\\"\\u003e \\u003cp\\u003e80\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e100\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.37\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e0.46\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\" morerows=\\\"1\\\" rowspan=\\\"2\\\"\\u003e \\u003cp\\u003e200\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.43\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e2.77\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.01\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1.25\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\" morerows=\\\"2\\\" rowspan=\\\"3\\\"\\u003e \\u003cp\\u003e400\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.02\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e3.32\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.20\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1.93\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e14\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.18\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1.78\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\" morerows=\\\"1\\\" rowspan=\\\"2\\\"\\u003e \\u003cp\\u003e85\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e200\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.13\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e0.26\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e400\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.34\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1.23\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003c/table\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab6\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 5\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eTest results of collapse index and potential for samples stabilized with 7% colloidal silica concentration\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"6\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c6\\\" colnum=\\\"6\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eRelative compaction (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eInundation stress (kPa)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eCuring time (day)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eInitial moisture content (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003eCollapse index (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eCollapse potential\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\" morerows=\\\"5\\\" rowspan=\\\"6\\\"\\u003e \\u003cp\\u003e80\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e100\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e14.99\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e0.12\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\" morerows=\\\"1\\\" rowspan=\\\"2\\\"\\u003e \\u003cp\\u003e200\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e14.84\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1.74\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.26\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e0.89\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\" morerows=\\\"2\\\" rowspan=\\\"3\\\"\\u003e \\u003cp\\u003e400\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.41\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e2.34\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eMedium\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.25\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1.22\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e14\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.03\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e0.97\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\" morerows=\\\"1\\\" rowspan=\\\"2\\\"\\u003e \\u003cp\\u003e85\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e200\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.11\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e0.12\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e400\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e15.14\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e0.99\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eNegligible\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003c/table\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003cp\\u003eTable 6. Test results of collapse index and potential for samples stabilized with 10% colloidal silica concentration\\u003c/p\\u003e\\n\\u003cdiv\\u003e\\n \\u003ctable dir=\\\"rtl\\\" border=\\\"1\\\" cellspacing=\\\"0\\\" cellpadding=\\\"0\\\"\\u003e\\n \\u003ctbody\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 109px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eCollapse potential\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 91px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eCollapse index (%)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eInitial moisture content (%)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eCuring time (day)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eInundation stress (kPa)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eRelative compaction (%)\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 109px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eNon collapsible\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 91px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e0.08\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e15.23\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e1\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e100\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd rowspan=\\\"6\\\" style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e80\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 109px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eNegligible\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 91px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e1.36\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e14.85\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e1\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd rowspan=\\\"2\\\" style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e200\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 109px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eNegligible\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 91px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e0.77\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e15.28\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e7\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 109px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eNegligible\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 91px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e2.04\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e15.17\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e1\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd rowspan=\\\"3\\\" style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e400\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 109px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eNegligible\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 91px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e1.05\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e15.42\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e7\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 109px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eNegligible\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 91px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e0.71\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e14.92\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e14\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 109px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eNon collapsible\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 91px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e0.03\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e15.11\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e1\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e200\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd rowspan=\\\"2\\\" style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e85\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd style=\\\"width: 109px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003eNegligible\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 91px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e0.52\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e15.39\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e1\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd style=\\\"width: 100px;\\\"\\u003e\\n \\u003cp dir=\\\"LTR\\\"\\u003e400\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003c/tbody\\u003e\\n \\u003c/table\\u003e\\n\\u003c/div\\u003e\\u003c/br\\u003e\\u003cp\\u003eAs illustrated in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e, for a relative compaction of 80% and a curing time of one day, an increase in the stress level from 100 kPa to 200 kPa and subsequently to 400 kPa leads to a corresponding rise in soil collapse for various concentrations of CS. Specifically, the collapse potential increases as follows: with 3% CS, from 1.45 to 3.65 and then to 5.04%; with 5% CS, from 0.46 to 2.77 and then to 3.32%; with 7% CS, from 0.12 to 1.74and then to 2.34%; and with 10% CS, from 0.08 to 1.36 and then to 2.04%.\\u003c/p\\u003e\\u003cp\\u003eFor a relative compaction of 80% and a curing time of 7 days, it is observed that with an increase in the stress level from 200 to 400 kPa, the soil collapse for concentrations of 3, 5, 7 and 10% CS, increases from 2.24 to 4.25%, from 1.25 to 1.93%, from 0.89 to 1.22% and from 0.77 to 1.05%, respectively (see Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003e).\\u003c/p\\u003e\\u003cp\\u003eAl-Juari (\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e2009\\u003c/span\\u003e) conducted a study on undisturbed samples with a dry unit weight of 14.91 kN/m\\u0026sup3; and found that soil collapse is positively correlated with increasing levels of inundation stress. Also, Haeri et al (\\u003cspan citationid=\\\"CR16\\\" class=\\\"CitationRef\\\"\\u003e2012\\u003c/span\\u003e), reported same results for the remolded loessal soil samples.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec14\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e3.1.3. Effect of curing time on the collapsibility\\u003c/h2\\u003e \\u003cp\\u003eAs can be seen from Tables\\u0026nbsp;\\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e\\u0026ndash;\\u003cspan refid=\\\"Tab3\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003e, in general, the collapse index and collapse potential of the studied soil decrease with increasing curing time. Tests conducted on samples made with 80% density under 100 kPa stress show that the collapse potential is reduced to an acceptable level after a one-day curing time. Also, in samples made with a relative compaction of 85%, the collapse index and potential under 400 kPa stress and one-day curing time also decrease to a negligible degree of collapsibility. For this reason, the effect of curing time is omitted for these two cases.\\u003c/p\\u003e \\u003cp\\u003eAs can be seen in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig7\\\" class=\\\"InternalRef\\\"\\u003e7\\u003c/span\\u003e, the collapse index for samples made with a relative compaction of 80% and 3% concentration decreases from 3.65 to 2.24 and 1.69%, respectively, with an increase in curing time from one to 7 and 14 days. Also, for concentrations of 5, 7 and 10%, with an increase in curing time from one to 7 days, the collapse index decreases from 2.77 to 1.25%, from 1.74 to 0.89% and from 1.36 to 0.77%, respectively.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eThe results of the collapse potential tests conducted under a stress of 400 kPa, as depicted in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig8\\\" class=\\\"InternalRef\\\"\\u003e8\\u003c/span\\u003e, reveal that for samples with a relative compaction of 80% and 3% colloidal silica concentration, the collapse potential decreases progressively with increasing curing time. Specifically, the collapse potential reduces from 5.04 at one day to 4.25 at 7 days, 4.02 at 14 days, and further to 3.74% at 28 days. Similarly, for higher concentrations of colloidal silica (5, 7, and 10%), the collapse potential also decreases significantly with extended curing time. For a 5% concentration, the collapse potential declines from 2.32 at one day to 1.93 at 7 days and 1.78% at 14 days. For a 7% concentration, it decreases from 2.34at one day to 1.22 at 7 days and 0.97% at 14 days. Finally, for a 10% concentration, the collapse potential drops from 2.04 at one day to 1.05 at 7 days and 0.71% at 14 days.\\u003c/p\\u003e\\u003cp\\u003eThe reason for this is that as the curing time increases, the formed gel turns into a solid and the bond between soil particles becomes stronger. Further explanations on this subject are provided in section \\u003cspan refid=\\\"Sec21\\\" class=\\\"InternalRef\\\"\\u003e3.3\\u003c/span\\u003e.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec15\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e3.1.4. Effect of CS concentration on the collapsibility\\u003c/h2\\u003e \\u003cp\\u003eThe colloidal silica concentration is the weight ratio of nano-silica particles to colloidal silica solution. In general, based on Tables\\u0026nbsp;\\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e\\u0026ndash;\\u003cspan refid=\\\"Tab3\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003e, as the colloidal silica concentration increases, the collapse index and potential decrease. The reason for this is that as the colloidal silica concentration increases, the formed gel becomes stiffer.\\u003c/p\\u003e \\u003cp\\u003eAlthough it is not possible to form a hard gel from a colloidal silica solution with a concentration of 3% [7], studies were nevertheless conducted with this concentration to evaluate the effect of low concentrations of colloidal silica on the behavior of collapsible soil. The results showed that in samples made with a relative compaction of 80%, 3% concentration and one day curing time, the collapse potential under 100 kPa stress resulted in a negligible collapse degree. It was also observed in samples made with a relative compaction of 80%, 3% concentration under 200 kPa stress that with increasing curing time from one to 14 days, the collapse index reached a negligible collapse degree (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig9\\\" class=\\\"InternalRef\\\"\\u003e9\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eFor samples made with a relative compaction of 80%, the collapse potential under a stress of 400 kPa reaches a moderate degree of collapsibility by a curing time of 14 days, but the collapse in this case is more than the permissible limit. For this reason, the collapse potential of the sample stabilized with a concentration of 3% and a curing time of 28 days is also examined. As shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig10\\\" class=\\\"InternalRef\\\"\\u003e10\\u003c/span\\u003e, with an increase in the curing time to 28 days, the collapse potential reaches 3.73%. This value is also more than the permissible limit.\\u003c/p\\u003e \\u003cp\\u003eUpon increasing the colloidal silica concentration to 5%, it was observed that the collapse potential under a stress of 100 kPa reached 0.46% after one day of curing. Furthermore, the collapse index increased to 1.25% after 7 days of curing. Similarly, under a stress of 400 kPa, the collapse potential was found to be 1.93% after 7 days of curing. Based on the findings of this study, the optimal concentration of stabilizer required to mitigate collapsibility is determined to be 5%. For concentrations exceeding 5%, both the collapse index and collapse potential were observed to decrease to acceptable levels as curing time increased.\\u003c/p\\u003e \\u003cp\\u003eIn a study conducted by Wong et al. (\\u003cspan citationid=\\\"CR31\\\" class=\\\"CitationRef\\\"\\u003e2018\\u003c/span\\u003e), it was reported that the settlement of kaolinite clay stabilized with colloidal silica is significantly lower compared to that of unstabilized kaolinite clay. Therefore, it can be concluded that, in addition to filling the soil's void spaces with colloidal silica, an increase in the concentration of colloidal silica results in the formation of a stiffer gel. Over time, the gel produced from the colloidal silica solution undergoes further solidification, transforming into a more rigid structure. Consequently, the collapsibility of soil stabilized with colloidal silica is significantly reduced.\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec16\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e3.2. Results of UCS tests\\u003c/h2\\u003e \\u003cp\\u003eThe results of the unconfined compressive strength (UCS) tests are presented and analyzed hereunder. The investigation focuses on the influence of key parameters, including colloidal silica concentration and curing time, on the observed outcomes.\\u003c/p\\u003e \\u003cdiv id=\\\"Sec17\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e3.2.1. Effect of colloidal silica concentration on the UCS\\u003c/h2\\u003e \\u003cp\\u003eAs illustrated in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig11\\\" class=\\\"InternalRef\\\"\\u003e11\\u003c/span\\u003e, the addition of colloidal silica to the soil leads to an increase in the unconfined compressive strength (UCS). This improvement can be attributed to the ability of colloidal silica to fill the void spaces within the soil matrix and effectively bind the soil particles together. Furthermore, the results demonstrate that, at a constant curing time, the UCS of the samples increases with higher concentrations of colloidal silica. The primary mechanism underlying this enhancement is the increased stiffness of the gel formed as the concentration of colloidal silica rises, which contributes to the overall strengthening of the soil structure. Similar results were reported for sandy soil by Persoff et al. (\\u003cspan citationid=\\\"CR26\\\" class=\\\"CitationRef\\\"\\u003e1999\\u003c/span\\u003e). Another observation that can be drawn from Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig11\\\" class=\\\"InternalRef\\\"\\u003e11\\u003c/span\\u003e is that, at a curing time of 14 days, the strength of the sample stabilized with a 7% colloidal silica concentration achieved approximately 84% of the strength exhibited by the sample stabilized with a 10% concentration. Based on these results, it can be concluded that the optimal colloidal silica concentration, as determined through the unconfined compression test, is 7%.\\u003c/p\\u003e\\u003c/div\\u003e \\u003cdiv id=\\\"Sec18\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e3.2.2. Effect of curing time on the UCS\\u003c/h2\\u003e \\u003cp\\u003eAs depicted in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig12\\\" class=\\\"InternalRef\\\"\\u003e12\\u003c/span\\u003e, the UCS of samples stabilized with colloidal silica increases with prolonged curing time. For instance, at a colloidal silica concentration of 7%, the UCS increases by approximately 19% when the curing time is extended to 7 days. Similarly, an additional increase of about 20% is observed when the curing time is further extended from 7 to 14 days, and a subsequent increase of approximately 16% occurs when the curing time is extended from 14 to 28 days. This progressive enhancement in UCS can be attributed to the gradual transformation of the colloidal silica gel into a solid body over time, which contributes to the strengthening of the soil matrix.\\u003c/p\\u003e\\u003cp\\u003eAs observed, the samples stabilized with colloidal silica attain the majority of their strength by the 14-day curing time, with the rate of strength increase diminishing thereafter. Given that the initial setting time for the colloidal silica solution is approximately two hours, it can be inferred that the optimal curing time for achieving robust mechanical performance is 14 days, which corresponds to 168 times the gelation time.\\u003c/p\\u003e \\u003cp\\u003eWhen clay is left undisturbed after being remolded, without any change in its moisture content, it has the potential to recover its lost strength over time. This phenomenon is referred to as thixotropy. However, as illustrated in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig12\\\" class=\\\"InternalRef\\\"\\u003e12\\u003c/span\\u003e, the increase in strength over time in untreated samples is minimal. This can be attributed to the fact that the soil under investigation in this study is kaolinite clay, which exhibits very limited thixotropic behavior. Previous research on the thixotropic properties of clay minerals, including kaolinite, illite, and montmorillonite, has demonstrated that kaolinite displays almost negligible thixotropic characteristics (Skempton and Nothey, 1952).\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec19\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e3.2.3. Effect of colloidal silica on the stress-strain curve of soil and its brittleness\\u003c/h2\\u003e \\u003cp\\u003eTo evaluate the effect of colloidal silica on the behavior of soil at the Golestan Dam construction site, this material was added to the soil at concentrations of 3, 5, 7, and 10%. The samples were prepared at the optimum moisture content and subjected to curing times of one, 7, 14, and 28 days. Subsequently, unconfined compression tests were conducted on the treated samples. Figures\\u0026nbsp;\\u003cspan refid=\\\"Fig13\\\" class=\\\"InternalRef\\\"\\u003e13\\u003c/span\\u003ea to d, illustrate the stress-strain curves of the stabilized soil, showcasing the effects of varying colloidal silica concentrations across different curing times.\\u003c/p\\u003e\\u003cp\\u003eAs illustrated in Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig13\\\" class=\\\"InternalRef\\\"\\u003e13\\u003c/span\\u003ea to d, the UCS increases significantly with an increase in colloidal silica concentration. Furthermore, for a given concentration of colloidal silica, the UCS is observed to increase progressively with curing time.\\u003c/p\\u003e \\u003cp\\u003eAdditionally, as depicted in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig13\\\" class=\\\"InternalRef\\\"\\u003e13\\u003c/span\\u003e, the peak of UCS of the stabilized soil occurs at a slightly lower strain in all specimens compared to the untreated soil. Therefore, it can be concluded that this treatment enhances both the stiffness and UCS of the soil without inducing significant brittle behavior.\\u003c/p\\u003e \\u003cp\\u003eThe brittleness index is defined as the normalized difference between the maximum and residual strength, calculated by dividing this difference by the maximum strength (Eq.\\u0026nbsp;\\u003cspan refid=\\\"Equ2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e) (Ta'negonbadi and Noorzad, \\u003cspan citationid=\\\"CR30\\\" class=\\\"CitationRef\\\"\\u003e2017\\u003c/span\\u003e). This dimensionless index ranges from zero to one, where a value of zero signifies complete flexibility or non-brittleness of the sample, while a value of one indicates complete brittleness. Furthermore, this index serves as an indicator of soil contractiveness and the intensity of strain softening behavior:\\u003cdiv id=\\\"Equ2\\\" class=\\\"Equation\\\"\\u003e\\u003cdiv format=\\\"TEX\\\" class=\\\"mathdisplay\\\" id=\\\"FileID_Equ2\\\" name=\\\"EquationSource\\\"\\u003e\\n$$\\\\:{I}_{B}=({q}_{p}-{q}_{r})/{q}_{p}$$\\u003c/div\\u003e\\u003cdiv class=\\\"EquationNumber\\\"\\u003e2\\u003c/div\\u003e\\u003c/div\\u003e\\u003c/p\\u003e \\u003cp\\u003ewhere \\u003cem\\u003eq\\u003c/em\\u003e\\u003csub\\u003e\\u003cem\\u003ep\\u003c/em\\u003e\\u003c/sub\\u003e​ and \\u003cem\\u003eq\\u003c/em\\u003e\\u003csub\\u003e\\u003cem\\u003er\\u003c/em\\u003e\\u003c/sub\\u003e​ represent the peak and residual strengths, respectively, as determined from the unconfined compression test. A comparative analysis was conducted between untreated and colloidal silica (CS)-treated soil samples. The brittleness indices of these samples were calculated and summarized in Table\\u0026nbsp;\\u003cspan refid=\\\"Tab7\\\" class=\\\"InternalRef\\\"\\u003e7\\u003c/span\\u003e. It was observed that the CS treatment did not result in a significant change in the brittleness index. Figure\\u0026nbsp;\\u003cspan refid=\\\"Fig14\\\" class=\\\"InternalRef\\\"\\u003e14\\u003c/span\\u003e illustrates the failure mode of both the unstabilized sample and the sample stabilized with 7% colloidal silica. Immediately after reaching the maximum strength, a shear band forms, followed by a sudden loss of strength, indicative of brittle failure. As observed, the failure angle in both the unstabilized and stabilized samples is similar, approximating 45 degrees.\\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab7\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 7\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eResults of the unconfined compression test and brittleness index for untreated and treated samples at various curing times\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"6\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"char\\\" char=\\\".\\\" class=\\\"colspec\\\" colname=\\\"c6\\\" colnum=\\\"6\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eSample code\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eColloidal silica concentration (%)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eCuring time (day)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003ePeak strength (kP)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" 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morerows=\\\"4\\\" rowspan=\\\"5\\\"\\u003e \\u003cp\\u003e7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e128.47\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e23.44\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e0.82\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eCL-3-7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e3\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e213.25\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e34.39\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e0.84\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eCL-5-7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e5\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e291.45\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e45.87\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e0.84\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eCL-7-7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e 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colname=\\\"c6\\\"\\u003e \\u003cp\\u003e0.86\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eCL-0-14\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e0\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\" morerows=\\\"4\\\" rowspan=\\\"5\\\"\\u003e \\u003cp\\u003e14\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e131.58\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e22.22\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e0.83\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e 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colname=\\\"c5\\\"\\u003e \\u003cp\\u003e46.67\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e0.86\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eCL-7-14\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e7\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e390.63\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e50.48\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e0.87\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eCL-10-14\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e10\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e464.54\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e56.26\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e0.88\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eCL-0-28\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e0\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c3\\\" morerows=\\\"4\\\" rowspan=\\\"5\\\"\\u003e \\u003cp\\u003e28\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"char\\\" char=\\\".\\\" colname=\\\"c4\\\"\\u003e 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\\u003c/p\\u003e \\u003cp\\u003eHowever, the unconfined compression test revealed that as the CS concentration increased from 0 to 10%, the peak axial stress increased from 122 kPa to 505 kPa, corresponding to a maximum increment of up to 314%. These findings underscore the effectiveness of CS stabilization in enhancing the mechanical properties of this soil.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec20\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003e3.2.4. Effect of colloidal silica on the secant modulus of deformation and absorbed energy\\u003c/h2\\u003e \\u003cp\\u003eThe secant modulus of deformation (E\\u003csub\\u003e50\\u003c/sub\\u003e) in the unconfined compression test is determined by calculating the slope of the line in the stress-strain curve. Specifically, the point corresponding to 50% of the peak strength is identified and connected to the origin of the coordinate system. The strain corresponding to this point is then calculated, and the resulting slope of the line provides the value of the secant modulus (E\\u003csub\\u003e50\\u003c/sub\\u003e).\\u003c/p\\u003e \\u003cp\\u003eFigure \\u003cspan refid=\\\"Fig15\\\" class=\\\"InternalRef\\\"\\u003e15\\u003c/span\\u003e illustrates the variations in the secant modulus (E\\u003csub\\u003e50\\u003c/sub\\u003e) as a function of colloidal silica concentration at different curing times. From this figure, it is evident that the secant modulus increases significantly with prolonged curing time. For instance, in the case of a sample stabilized with a 5% colloidal silica concentration, the E\\u003csub\\u003e50\\u003c/sub\\u003e value is observed to increase by approximately 48% when the curing time is extended from one to 28 days. This phenomenon can be attributed to the transformation of the colloidal silica gel into a solid phase over time. Consequently, both the strength of the material and the associated secant modulus are enhanced.\\u003c/p\\u003e\\u003cp\\u003eAbsorbed energy represents the amount of energy required to deform a material. In an unconfined compression test, the absorbed energy is determined by calculating the area under the stress-strain curve at a specified strain (e.g., 15%). Figure\\u0026nbsp;\\u003cspan refid=\\\"Fig16\\\" class=\\\"InternalRef\\\"\\u003e16\\u003c/span\\u003e presents the graph of absorbed energy as a function of curing time for various concentrations of colloidal silica. As observed, at a constant curing time, the absorbed energy increases with higher concentrations of colloidal silica. Additionally, for a given concentration, the absorbed energy rises as the curing time is extended. This increase in absorbed energy can be attributed to the enhancement in soil strength, which, in turn, leads to an expansion in the area under the stress-strain curve.\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec21\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e3.3. Effect on microstructure\\u003c/h2\\u003e \\u003cp\\u003eThe SEM micrographs were utilized to gain a deeper understanding of the effects of colloidal silica (CS) and to analyze the microstructural characteristics of both untreated and CS-treated soils. Figure\\u0026nbsp;\\u003cspan refid=\\\"Fig17\\\" class=\\\"InternalRef\\\"\\u003e17\\u003c/span\\u003e present scanning electron microscope (SEM) images of both unstabilized and colloidal silica-stabilized soil samples, captured at a magnification of 500x. As previously discussed, collapsible soils exhibit an open and semi-stable structure, which accounts for the visible voids between soil particles in the unstabilized sample. These voids are highlighted by red circles in the corresponding images. In contrast, the SEM image of the stabilized sample reveals that the colloidal silica gel effectively fills the interstitial spaces between soil particles, promoting inter-particle bonding and enhancing the overall structural integrity.\\u003c/p\\u003e\\u003cp\\u003eBy stabilization of the soil, its structure undergoes significant changes as a result of the chemical reactions between the soil and the colloidal silica mixture, which lead to the formation of gel. A comparison of Figs.\\u0026nbsp;\\u003cspan refid=\\\"Fig17\\\" class=\\\"InternalRef\\\"\\u003e17\\u003c/span\\u003ea,b highlights a substantial transformation in the soil's structure. It is evident that the untreated soil, which initially exhibits a grain-based structure in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig17\\\" class=\\\"InternalRef\\\"\\u003e17\\u003c/span\\u003ea, transitions to a more aggregated form in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig17\\\" class=\\\"InternalRef\\\"\\u003e17\\u003c/span\\u003eb. This change can be attributed to the chemical reactions and the production of colloidal silica gel, which alter the soil's structure.\\u003c/p\\u003e \\u003c/div\\u003e\"},{\"header\":\"4. Conclusion\",\"content\":\"\\u003cp\\u003eIn this reaearch, colloidal silica effect on the stabilization of collapsible soil was investigated. The most important results of the tests can be summarized as following cases:\\u003c/p\\u003e \\u003cp\\u003e \\u003col\\u003e \\u003cspan\\u003e \\u003cli\\u003e \\u003cp\\u003eThe addition of colloidal silica to the collapsible soil investigated in this study resulted in a reduction in both the collapse index and collapse potential. This improvement can be attributed to the gel formed from the colloidal silica solution, which effectively fills the voids between soil particles, thereby reducing soil compressibility. The optimal concentration for mitigating soil collapsibility was found to be 5%, as it successfully reduced the collapse potential from severe to negligible levels.\\u003c/p\\u003e \\u003c/li\\u003e \\u003c/span\\u003e \\u003cspan\\u003e \\u003cli\\u003e \\u003cp\\u003eThe results of the collapsibility tests indicated that as the relative compaction increased from 80 to 85%, both the collapse potential and collapse index of the unstabilized and CS-stabilized samples decreased.\\u003c/p\\u003e \\u003c/li\\u003e \\u003c/span\\u003e \\u003cspan\\u003e \\u003cli\\u003e \\u003cp\\u003eOne of the key factors influencing the collapsibility of stabilized soil is the curing time. Research has demonstrated that as the curing time increases, both the collapse index and collapse potential decrease. This reduction can be attributed to the gradual transformation of the gel formed by the colloidal silica solution into a solid state over time.\\u003c/p\\u003e \\u003c/li\\u003e \\u003c/span\\u003e \\u003cspan\\u003e \\u003cli\\u003e \\u003cp\\u003eThe test results demonstrated that soil collapsibility increases with rising inundation stress levels, specifically from 100 kPa to 200 kPa and further to 400 kPa. Consequently, it can be inferred that an increase in the inundation stress level is associated with a corresponding intensification of soil collapsibility.\\u003c/p\\u003e \\u003c/li\\u003e \\u003c/span\\u003e \\u003cspan\\u003e \\u003cli\\u003e \\u003cp\\u003eThe addition of colloidal silica to the soil resulted in an increase in its unconfined compressive strength (UCS); however, no significant change was observed in the failure strain. The UCS was found to increase with higher concentrations of colloidal silica, as the gel formed becomes progressively stiffer. At a curing time of 14 days, the strength of the sample stabilized with a 7% colloidal silica concentration reached approximately 84% of the strength of the sample stabilized with a 10% concentration. Based on these findings, it can be concluded that the optimal colloidal silica concentration, as determined by the unconfined compression test, is 7%.\\u003c/p\\u003e \\u003c/li\\u003e \\u003c/span\\u003e \\u003cspan\\u003e \\u003cli\\u003e \\u003cp\\u003eBased on the stress-strain curves of UCS tests, it is observed that this stabilization increases both the stiffness and UCS of the soil without leading to a considerable brittle behavior.\\u003c/p\\u003e \\u003c/li\\u003e \\u003c/span\\u003e \\u003cspan\\u003e \\u003cli\\u003e \\u003cp\\u003eIn general, as the curing time increases from 1 to 28 days, the unconfined compressive strength (UCS) of the samples also increases. However, the rate of strength gain diminishes after a curing period of 14 days. Consequently, the optimal curing age for achieving maximum strength in the stabilized samples is 14 days. The observed increase in strength in samples stabilized with colloidal silica can be attributed to the progressive solidification of the colloidal silica gel over time.\\u003c/p\\u003e \\u003c/li\\u003e \\u003c/span\\u003e \\u003cspan\\u003e \\u003cli\\u003e \\u003cp\\u003eThe SEM image of the unstabilized soil demonstrates that the collapsible soil structure is open and semi-stable, characterized by visible voids between soil particles. In contrast, the SEM micrograph of the treated soil indicates that the colloidal silica gel successfully fills the interstitial spaces between soil particles. This filling effect promotes inter-particle bonding, thereby significantly enhancing the overall structural integrity of the soil.\\u003c/p\\u003e \\u003c/li\\u003e \\u003c/span\\u003e \\u003c/ol\\u003e \\u003c/p\\u003e \"},{\"header\":\"Declarations\",\"content\":\"\\u003ch2\\u003eFunding\\u003c/h2\\u003e \\u003cp\\u003eThe research presented in this paper was financially supported by Babol Noshirvani University of Technology through grant program of BNUT/370723/03.\\u003c/p\\u003e\\u003ch2\\u003eAuthor Contribution\\u003c/h2\\u003e\\u003cp\\u003eThe authors contributed to this work as follows:Fatemeh Bakhshandeh : Conceptualization, Methodology, Investigation, Writing \\u0026ndash; Original Draft Preparation.Reza Noorzad : Supervision, Conceptualization, Methodology, Validation, Review \\u0026amp; Editing.Bahram Ta'negonbadi : Conceptualization, Writing \\u0026ndash; Review \\u0026amp; Editing.All authors have read and approved the final version of the manuscript and agree to be accountable for all aspects of the work.\\u003c/p\\u003e\\u003ch2\\u003eData Availability\\u003c/h2\\u003e\\u003cp\\u003eAll data generated or analyzed during this study are included in the paper.\\u003c/p\\u003e\\n\\u003ch2\\u003eAdditional Information\\u003c/h2\\u003e\\n\\u003cp\\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\n\\u003cli\\u003eAl-Juari, K.A., 2009. Volume change measurement of collapsible soil stabilized with lime and waste lime. Tikrit Journal of Engineering Sciences, 16(3), pp.38-54.\\u003c/li\\u003e\\n\\u003cli\\u003eAl-Obaidi, Q.A., Ibrahim, S.F. and Schanz, T., 2013. Evaluation of collapse potential investigated from different collapsible soils. In Multiphysical testing of soils and shales (pp. 117-122). Springer Berlin Heidelberg.\\u003c/li\\u003e\\n\\u003cli\\u003eASTM D-2166, 2024. Standard Test Method for Unconfined Compressive Strength of Cohesive Soil. Annual Book of ASTM Standards, USA.\\u003c/li\\u003e\\n\\u003cli\\u003eASTM D-2487, 2017. Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System). Annual Book of ASTM Standards, USA.\\u003c/li\\u003e\\n\\u003cli\\u003eASTM D-4318, 2017. Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils. Annual Book of ASTM Standards, USA.\\u003c/li\\u003e\\n\\u003cli\\u003eASTM D-5333, 2017. 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Experimental investigations of colloidal silica grouting in porous media. Journal of geotechnical and geoenvironmental engineering, 135(5), pp.697-700.\\u003c/li\\u003e\\n\\u003cli\\u003eCerato, A.B., Miller, G.A. and Hajjat, J.A., 2009. Influence of clod-size and structure on wetting-induced volume change of compacted soil. Journal of geotechnical and geoenvironmental engineering, 135(11), pp.1620-1628.\\u003c/li\\u003e\\n\\u003cli\\u003eFang, H.Y., 2013. Foundation engineering handbook. Springer Science \\u0026amp; Business Media. \\u003c/li\\u003e\\n\\u003cli\\u003eGallagher, P.M., Pamuk, A. and Abdoun, T., 2007. Stabilization of liquefiable soils using colloidal silica grout. Journal of Materials in Civil Engineering, 19(1), pp.33-40.\\u003c/li\\u003e\\n\\u003cli\\u003eGeorgiannou, V.N., Pavlopoulou, E.M. and Bikos, Z., 2017. Mechanical behaviour of sand stabilised with colloidal silica. Geotechnical Research, 4(1), pp.1-11.\\u003c/li\\u003e\\n\\u003cli\\u003eHaeri, S.M., Zamani, A. and Garakani, A.A., 2012. Collapse potential and permeability of undisturbed and remolded loessial soil samples. In Unsaturated Soils: Research and Applications: Volume 1 (pp. 301-308). Springer Berlin Heidelberg.\\u003c/li\\u003e\\n\\u003cli\\u003eHouston, S.L., Houston, W.N. and Mahmoud, H.H., 1995. Interpretation and comparison of collapse measurement techniques. In Genesis and properties of collapsible soils (pp. 217-224). Dordrecht: Springer Netherlands.\\u003c/li\\u003e\\n\\u003cli\\u003eHouston, S.L., Houston, W.N., Zapata, C.E. and Lawrence, C., 2001. Geotechnical engineering practice for collapsible soils. Geotechnical \\u0026amp; Geological Engineering, 19, pp.333-355.\\u003c/li\\u003e\\n\\u003cli\\u003eKakavand, A. and Dabiri, R., 2018. Experimental study of applying colloidal nano Silica in improving sand-silt mixtures. International Journal of Nano Dimension, 9(4), pp.357-373. \\u003c/li\\u003e\\n\\u003cli\\u003eKrishnan, J., Sharma, P. and Shukla, S., 2021. Experimental investigations on the mechanical properties of sand stabilized with colloidal silica. Iranian Journal of Science and Technology, Transactions of Civil Engineering, 45, pp.1737-1758.\\u003c/li\\u003e\\n\\u003cli\\u003eLin, Y., 2006. Colloidal silica transport mechanisms for passive site stabilization of liquefiable soils. Drexel University.\\u003c/li\\u003e\\n\\u003cli\\u003eMahmood, M.S. and Abrahim, M.J., 2021, February. A review of collapsible soils behavior and prediction. In IOP Conference Series: Materials Science and Engineering (Vol. 1094, No. 1, p. 012044). IOP Publishing.\\u003c/li\\u003e\\n\\u003cli\\u003eNoorzad, R. and Nouri Delavar, I., 2019. Investigation into the short-term behavior of silty sand stabilized with colloidal silica. Scientia Iranica, 26(3), pp.1206-1213.\\u003c/li\\u003e\\n\\u003cli\\u003eNoorzad, R. and Pakniat, H., 2016. Investigating the effect of sample disturbance, compaction and stabilization on the collapse index of soils. Environmental Earth Sciences, 75, pp.1-9.\\u003c/li\\u003e\\n\\u003cli\\u003ePedrotti, M., Wong, C., El Mountassir, G., Renshaw, J.C. and Lunn, R.J., 2020. Desiccation behaviour of colloidal silica grouted sand: A new material for the creation of near surface hydraulic barriers. Engineering Geology, 270, p.105579.\\u003c/li\\u003e\\n\\u003cli\\u003ePersoff, P., Apps, J., Moridis, G. and Whang, J.M., 1999. Effect of dilution and contaminants on sand grouted with colloidal silica. Journal of geotechnical and geoenvironmental engineering, 125(6), pp.461-469.\\u003c/li\\u003e\\n\\u003cli\\u003eRollins, K.M. and Kim, J., 2010. Dynamic compaction of collapsible soils based on US case histories. Journal of geotechnical and geoenvironmental engineering, 136(9), pp.1178-1186.\\u003c/li\\u003e\\n\\u003cli\\u003eSeif, M.E., MolaAbasi, H., Saba, H. and Mirhosseini, S.M., 2024. Investigating the impact of nano-colloidal silica on sandy clay strength: Experimental results and stress-strain modeling insights. Construction and Building Materials, 438, p.137105.\\u003c/li\\u003e\\n\\u003cli\\u003eSkempton, A.W. and Northey, R.D., 1952. The sensitivity of clays. Geotechnique, 3(1), pp.30-53.\\u003c/li\\u003e\\n\\u003cli\\u003eTa\\u0026apos;negonbadi, B. and Noorzad, R., 2017. Stabilization of clayey soil using lignosulfonate. Transportation Geotechnics, 12, pp.45-55.\\u003c/li\\u003e\\n\\u003cli\\u003eWong, C., Pedrotti, M., El Mountassir, G. and Lunn, R.J., 2018. A study on the mechanical interaction between soil and colloidal silica gel for ground improvement. Engineering geology, 243, pp.84-100.\\u003c/li\\u003e\\n\\u003c/ol\\u003e\"}],\"fulltextSource\":\"\",\"fullText\":\"\",\"funders\":[],\"hasAdminPriorityOnWorkflow\":false,\"hasManuscriptDocX\":true,\"hasOptedInToPreprint\":true,\"hasPassedJournalQc\":\"\",\"hasAnyPriority\":false,\"hideJournal\":false,\"highlight\":\"\",\"institution\":\"\",\"isAcceptedByJournal\":true,\"isAuthorSuppliedPdf\":false,\"isDeskRejected\":\"\",\"isHiddenFromSearch\":false,\"isInQc\":false,\"isInWorkflow\":false,\"isPdf\":false,\"isPdfUpToDate\":true,\"isWithdrawnOrRetracted\":false,\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"scientific-reports\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"scirep\",\"sideBox\":\"Learn more about [Scientific Reports](http://www.nature.com/srep/)\",\"snPcode\":\"\",\"submissionUrl\":\"\",\"title\":\"Scientific Reports\",\"twitterHandle\":\"\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"stoa\",\"reportingPortfolio\":\"Scientific Reports\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":true},\"keywords\":\"Colloidal Silica, Collapsible Soil, Soil Stabilization, Collapse Potential, Unconfined Compressive Strength\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-6655792/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-6655792/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003eCollapsible soils pose significant geotechnical challenges due to their tendency to exhibit high strength under natural moisture conditions but undergo substantial settlement upon wetting. To address this issue, various stabilizing agents, including lime, cement, silicates, resins, and acids, have been explored. This study investigates the effectiveness of colloidal silica (CS), a low-viscosity solution capable of forming a gel, as a stabilizing agent. Its unique properties enable it to be injected into or mixed directly with soil, offering versatility in application. The behavior of CS-stabilized collapsible soil was evaluated through collapse potential and unconfined compressive strength (UCS) tests. Scanning electron microscopy (SEM) was also conducted to analyze microstructural changes in untreated and CS-treated soils. Colloidal silica was added at concentrations of 3, 5, 7, and 10% by weight of dry soil, with curing times of one, 7, 14, and 28 days. Collapse potential tests were performed at relative compactions of 80 and 85%, while UCS tests used a relative compaction of 95%. Results indicated that colloidal silica significantly reduced soil collapsibility while enhancing stiffness and UCS without inducing brittleness. A 5% CS concentration was optimal, reducing collapsibility from severe to negligible. Increased relative compaction (80 to 85%) further decreased collapsibility, whereas higher inundation stress increased it. 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