Performance Analysis of Pipe-Jacking Waste Soils Solidified with Cement under Balanced Earth Pressure Conditions

Performance Analysis of Pipe-Jacking Waste Soils Solidified with Cement under Balanced Earth Pressure Conditions | 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 Performance Analysis of Pipe-Jacking Waste Soils Solidified with Cement under Balanced Earth Pressure Conditions Xu Youjun, Li Zhenyu, Chen Zhigang, Han Huichao, Yan Minghao This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4728114/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The utilization of pipe-jacking soil poses challenges due to its complex composition, which comprises polyacrylamide (PAM) and sodium bentonite (Na-Ben) surfactants, hindering drainage and solidification. Improper handling may induce environmental pollution. To address this problem, cement solidification was explored after modification with PAM and Na-Ben. By performing indoor resistance tests, freeze–thaw cycles, wet–dry cycles, SEM, XRD, and IR experiments, it was found that within certain ratios, cement solidification effectively stabilizes pipe-jacking waste soil. Specifically, PAM minimally impacts pipe-jacking waste-soil strength, whereas Na-Ben slightly reduces it. Microscopic analysis revealed that although water absorption hinders hydration reactions, PAM (at lower concentrations) promotes mineral particle cohesion during cement solidification. Na-Ben tends to aggregate, leading to uneven internal structure and inhibiting cementitious product formation Physical sciences/Engineering/Civil engineering Earth and environmental sciences/Environmental sciences/Environmental chemistry Pipe-jacking waste soil Recycled solidification filling material Mechanical properties Microstructural test Wet-dry test Freeze-thaw test 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 0. Introduction The pipe-jacking machine features precise control over direction and depth, maintains geological stability, minimizes surface disruption, and facilitates efficient construction, thereby providing crucial support for modern tunneling and pipeline installation [25] . However, ensuring controlled chamber pressure and the smooth discharge of pipe-jacking waste soil often requires the addition of various polymer materials, thus, the original soil can be enhanced to an ideal flowable state [1] . With the increasing implementation of pipe-jacking projects, corresponding environmental issues have emerged. The efficient utilization and treatment of muck after the addition of polymer modifiers have gradually attracted the attention of both academia and the engineering community. Traditionally, waste soil is typically disposed of by stacking or landfilling in abandoned mines [2] . Due to the incorporation of certain amounts of mineral-based bentonite and PAM materials, the muck forms a "plastic flow state," leading to reduced stacking heights and significantly increased land occupation. Waste soil generated from pipe jacking faces challenges in storage, handling, and utilization, with improper disposal methods potentially leading to ecological environmental pollution. Cement, a crucial building material, offers multiple advantages such as high strength, durability, resistance to pressure, and natural erosion. The material is cost-effective, easy to work with, and widely utilized in various construction and infrastructure projects. Researchers (both domestically and internationally) have explored the incorporation of cement into soil for resource utilization. For instance, Rui et al. [3] prepared a Controlled Low Strength Material (CLSM) by mixing muck with water, cement, fine sand, and fly ash in specific proportions, which can replace some conventional backfill materials. Wei et al. [4] investigated the blend of nanosilica with cementitious soil, thus demonstrating the favorable dynamic properties of this composite material. Jing et al. [5] combined Pisha sandstone with cement to create fill materials, effectively addressing soil management issues in their region. Zhang et al. [6] utilized recycled phosphogypsum and calcium aluminate cement, by mixing these materials with dredged soil, they obtained soil with enhanced properties after solidification. This material offers significant environmental sustainability, economic benefits, and engineering value. Ayawanna et al. [7] created a material by mixing steel slag, cement, and soil that exceeded standard acceptable values (0.6 MPa). Li et al. [8] mixed groove-cut soil with residues from calcination and fiber blended cement, which exhibited satisfactory performance. In summary, particularly for soil stabilization applications, cement exhibits potential effectiveness. However, pipe-jacking soil contains components such as polyacrylamide (PAM) and sodium bentonite (Na-Ben), which differ significantly in chemical composition from undisturbed soil. Currently, there is limited research on the applicability and effectiveness of cement-based stabilization methods specifically tailored for pipe-jacking waste soil. Therefore, this study proposes the utilization of cement for the solidification treatment of pipe-jacking muck. The researchers aim to investigate various factors influencing the solidification strength, analyze the microstructure of the solidified pipe-jacking soil, and study its resistance to freeze–thaw cycles and wet–dry durability. The anticipated research outcomes aim to provide scientific justification and technical guidance for the resource utilization of pipe-jacking soil as road base material, thereby promoting its practical application. 1. Experimental Materials and Methods 1.1 Experimental Objective According to the "Technical Code for Highway Pavement Base Construction JTG/T F20-2015" specifications, this study conducts indoor experiments to investigate the unconfined compressive strength, freeze–thaw durability, and wet–dry durability of cement-stabilized pipe-jacking muck. The research aims to reveal the microstructure of the stabilized waste soil and propose cementitious mix designs that meet the requirements for the road base materials specified in the code. This endeavor seeks to provide a foundation for the application of pipe-jacking waste soil in road subbase layers, thus promoting sustainable practices in civil engineering projects. 1.2 Experimental Materials The experimental soil is the original, unimproved pipe-jacking soil excavated during the introduction of reclaimed water in a metal deep processing industrial park in a certain city. The original appearance of the pipe-jacking soil is depicted in Figure 1. The soil type is fine sand, and the particle size distribution curve is depicted in Figure 2. The strata encountered during pipe jacking primarily comprises silty sand, with its physical and mechanical parameters detailed in Table 1. This type of stratum is characterized by low cohesive strength, a poor arching effect, and short self-stabilization time, which necessitates the addition of materials such as PAM solution and sodium-based bentonite to enhance the original slag soil to an ideal flowable state [9] , providing a crucial prerequisite for the smooth advancement of pipe-jacking operations. Table 1 Basic physical parameters of pipe-jacking residue Deformation modulus/（Mpa） Internal friction angle/（°） Cohesion/（Kpa） Natural density/（KN/m 3 ） Water content/% 8 30 0 19.5 6.8 This study proposes the utilization of cement for the solidification of the enhanced pipe-jacking waste soil. The main components of the enhanced material and the solidification material identified through X-ray fluorescence spectroscopy (XRF) are listed in Table 2. Table 2 Main chemical composition of test raw materials Raw materials Content of each component in the raw materials/% MgO Al 2 O 3 SiO 2 SO 3 Na 2 O K 2 O CaO TiO 2 Cl Cement 1.68 7.68 22.96 3.58 0.46 0.77 57.99 0.53 0.05 Pipe jacking spoil 2.51 13.28 63.72 0.16 1.82 2.59 8.88 0.87 0.03 Sodium-based bentonite 2.11 16.16 67.49 0.06 0.56 4.83 2.66 0.62 0.02 1.3 Experimental Procedure The experimental procedure is illustrated in Figure 3. 1.4 Determination of Mix Proportions According to reference [9] , a 0.2% concentration of PAM solution and a 9% concentration of sodium-based bentonite solution have exhibited satisfactory enhancement effects on pipe-jacking waste soil. Therefore, this study employs the same concentrations of additives as those listed in the reference, with 7% and 12% addition rates. At these concentrations, the modified slag soil exhibits a 169 cm slump value, thus demonstrating satisfactory workability [10] . A total of 10 test conditions were designed, as illustrated in Table 3. Table 3 Agent ratio Experiment ID Volume of cement added/% Volume of PAM solution added/% Volume of Na-Ben solution added/% Amount of water added/% C1 5 0 0 25 C2 6 0 0 25 C3 7 0 0 25 C4 8 0 0 25 C5 9 0 0 25 C6 5 12 7 6 C7 6 12 7 6 C8 7 12 7 6 C9 8 12 7 6 C10 9 12 7 6 To investigate the effects of PAM and sodium-based bentonite on cement solidification, the concentration of the original slag-soil improver solutions was varied under unchanged conditions, and a total of eight sets of experimental samples were designed as illustrated in Table 4. Table 4 Concentration ratio for the modifying solution Experiment ID Volume of cement added/% Concentration of PAM solution/% Concentration of Na-Ben solution/% Cd1 21 0.2 0 Cd2 21 0.4 0 Cd3 21 0.6 0 Cd4 21 0.8 0 Cd5 21 0 5 Cd6 21 0 10 Cd7 21 0 15 Cd8 21 0 20 1.5 Preparation and Curing of Specimens Following the "Test Code for Stabilized Materials of Highway Engineering Inorganic Binders" (JTG E51-2009), cylindrical specimens with dimensions of 150mm × 150mm × 150mm were prepared by casting, and indoor tests including compressive strength, freeze–thaw cycle, and dry–wet cycle were conducted. 1.6 Experimental Parameters The 7-day Unconfined Compressive Strength Requirements for Cementitious Road Base and Subbase Materials are detailed in tables 5 and 6 of the specifications. Table 5 Requirements of compressive strength for different grades of road subgrade Highway grade Exceedingly heavy traffic Heavy traffic Light traffic Expressways and Class I highways 4.0-5.0MPa 3.5-4.5Mpa 3.0-4.0Mpa Secondary and lower-level roads 3.5-4.5MPa 3.0-4.0Mpa 2.5-3.5Mpa Table 6 Requirements of compressive strength for the subbase of different grades of roads Highway grade Exceedingly heavy traffic Heavy traffic Light traffic Expressways and Class I highways 2.5-3.5Mpa 2.0-3.0Mpa 1.5-2.5Mpa Secondary and lower-level roads 2.0-3.0Mpa 1.5-2.5Mpa 1.0-2.0Mpa 2. Indoor Experimental Research on Solidified Pipe-Jacking Waste Soils 2.1 Analyzing Unconfined Compressive Strength To explore the influence of stabilizing agents on the unconfined compressive strength (UCS) of stabilized pipe-jacking waste soil, unconfined compressive strength tests were conducted under varying proportions of different stabilizing agents and stabilizing agent ratios. Based on Figure 4, under fixed ratios of sodium-based bentonite (Na-Ben) solution and polyacrylamide (PAM) solution, and with other conditions unchanged, increasing cement content leads to a moderate increase in the unconfined compressive strength (UCS) of cement-stabilized soil. However, within the analyzed ratio range, adding PAM solution and sodium-based bentonite (Na-Ben) leads to a decrease in the strength of cement-stabilized soil. The specific reasons are analyzed as follows: Impact of PAM: PAM, a high molecular weight polymer, exhibits strong water-absorption capabilities [11] . Within the studied ratio range, the polymer absorbs moisture, reducing the available water for cement-hydration reactions, thereby limiting hydration and reducing strength. Impact of sodium-based bentonite (Na-Ben): sodium-based bentonite (Na-Ben) is a clay mineral with significant water-absorbing and swelling capacities. Within the studied ratio range, its water-absorbing and swelling properties reduce the available moisture for cement-hydration reactions [12] , thus affecting the hydration process and structural formation of cementitious slurry, which leads to reduced strength. Changes in pore structure: The addition of PAM and sodium-based bentonite (Na-Ben) alters the pore structure of the cementitious slurry. The particles of sodium-based bentonite (Na-Ben) and molecules of PAM form larger pores or micro-cracks within the slurry [12] , weakening the overall structure of cement, thus reducing the material’s strength. Despite the reduction in strength due to the addition of PAM and sodium-based bentonite (Na-Ben), samples C5 and C10 still meet the strength requirements for sub-base materials of secondary highway pavements. Based on Figure 5, under constant cement ratios, the unconfined compressive strength of stabilized slag soil at 7 days and 28 days remains nearly consistent with increasing PAM solution concentrations. Therefore, the effect of PAM solution on cement stabilization is minimal, which can primarily be explained as follows: within the studied ratio range, polyacrylamide (PAM) does not promote the formation of hydration products and only mildly affects cement hydration due to its water-absorbing properties. However, it forms a viscous gel-like substance in water, which provides certain viscosity and adhesion [11] , thereby contributing to a modest increase in strength. Consequently, the material undergoes no significant macroscopic changes in strength. According to Figure 6, under constant proportions of the stabilizer, the unconfined compressive strength initially increases and subsequently decreases with increasing sodium-based bentonite concentration. This trend is primarily attributed to the characteristics of sodium-based bentonite, which, at lower concentrations, absorbs less water and fills some voids within the specimens, thereby enhancing their density and compressive strength. Additionally, after absorbing water, sodium-based bentonite forms colloids that possess adsorption capabilities [12] , thus stabilizing the structure by filling remaining voids post-cement hydration [13] . However, at higher concentrations, sodium-based bentonite induces uneven particle packing and the formation of more micro-pores within the specimens, thus reducing their density and strength [14] . Moreover, high concentrations of sodium-based bentonite absorb excessive moisture, leading to incomplete or less favorable cement hydration reactions, thereby impacting the formation of hydration products and subsequently affecting the specimens’ strength. 2.2 Analyzing Wet–Dry Cycling To investigate the impact of wet–dry cycles on the stabilized soil, dry–wet cycle tests were conducted using mixtures C4 and C9 and selected based on unconfined compressive strength experiments. CFM1 denotes the dry–wet cycle specimens for mixture C4, whereas CFM2 represents those for mixture C9. Based on Figure 8 and Figure7, the mass-loss rate gradually increases with the number of cycles. During the cycles, significant mass loss occurs, and an observation of the samples reveals that the top and bottom layers begin to spall after immersion, leading to considerable height reduction. Combining Figure 9 with Figure 4, it is evident that the compressive strength of the 28-day samples decreases as the number of cycles increases [15] , which is primarily occasioned by the influence of the wet–dry cycles on the hydration products in cement. Compounds such as ettringite and calcium aluminate hydrates, formed during cement hydration, undergo dissolution and precipitation cycles in the wet–dry process, gradually loosening the material’s structure and reducing its strength [16] . The resistance to wet–dry cycles is superior in sample CFM1 (mix C4) compared to CFM2 (mix C9). Although the polyacrylamide gel enhances the density and strength of CFM2 samples, during cement curing, the addition of PAM and sodium bentonite within the mixing range absorbs more moisture [17] . Moreover, sodium bentonite, within the mixing range, creates pores that affect strength formation. Therefore, CFM1 samples demonstrate more optimal performance in wet–dry cycle resistance. From the wet–dry cycle experiments, it is evident that the cement-stabilized slag exhibits slightly reduced resistance to wet–dry cycles compared to unstabilized slag within the mixing range. 2.3 Analyzing Freeze–Thaw Cycling Based on the compressive strength tests, CFM1 (representing mix C4) and CFM2 (representing mix C9) were selected for freeze–thaw cycle experiments. Figure 10 indicates that during the cycling process, CFM2 samples exhibited surface cracking and initial spalling. With increasing freeze–thaw cycles, the spalling increased gradually, eventually leading to substantial fragment detachment, making it difficult to maintain overall integrity. Contrastingly, CFM1 samples also experienced cracks and spalling, however, the detachment of small fragments was minimal, which enabled the overall shape to remain relatively intact. This difference is primarily attributed to the addition of PAM and sodium bentonite solutions in the CFM2 samples, which reduced the overall strength and diminished their resistance to freeze–thaw cycles. Based on Figure 11, it can be observed that the strength of mixes C4 and C9 decreases with an increase in freeze–thaw cycles at the age of 28 days. Sample C4 exhibits slightly more optimal freeze–thaw performance compared to C9, which is primarily explained as follows: when the moisture in cement freezes, it expands to occupy a region approximating its volume, exerting significant internal pressure within the concrete, thus leading to the formation or expansion of cracks. With repeated freeze–thaw cycles, these cracks multiply and expand, leading to structural damage and strength reduction. Within the specified range of ratios, the addition of PAM and sodium bentonite solutions during cement curing affects the hydration reaction of cement, with sodium bentonite increasing the number of cement structure cracks, leading to lower strength compared to specimens without added PAM. Figure 12 indicates that as the number of cycles increases, the mass loss gradually increases. This observation is mainly attributable to the freeze–thaw cycles that damage the microstructure of the concrete, thereby altering the structure of hydration products (such as ettringite and calcium hydroxide) in the cement paste, which further reduces its bonding capacity and overall strength. Additionally, freezing and thawing alter the in-concrete chemical environment [18] . For instance, during freezing, moisture from the cement paste is expelled from capillaries and re-enters during thawing, thus disrupting the cement hydration reaction through repeated processes. [19] From the freeze–thaw cycle experiments, it is evident that the frost resistance performance of cement-stabilized modified muck within the specified ratios is lower compared to the requirements of road-base materials. 3. Studying Microstructural Characteristics of Solidified Pipe-Jacking Waste Soils 3.1 XRD Experiment To further investigate the effect of additives in cement-stabilized pipe-jacking waste soil on the properties of stabilized muck, X-ray diffraction (XRD) experiments were conducted to analyze the mineral composition of stabilized muck. From Figure 13, it is evident that compared to sample C1, sample C4 exhibits prominent diffraction peaks at low angles (10°-30°), mainly composed of quartz (Qtz), albite (Ab), montmorillonite (Mrg), and C-S-H gel. Similarly, sample C9 also illustrates diffraction peaks at low angles, albeit with lower intensity, which indicates the presence of quartz (Qtz), albite (Ab), montmorillonite (Mrg), and C-S-H gel. Due to the addition of PAM and sodium bentonite in C9, these additives influence the cement hydration process, leading to a reduced generation of C-S-H gel. The XRD spectrum of C4 demonstrates a higher content of C-S-H gel, indicating a more thorough cement-hydration reaction. C-S-H gel is a primary contributor to cement strength, and its higher content directly enhances the sample's strength. Contrastingly, C9, due to the inclusion of PAM and sodium bentonite [20-21] , may adversely affect cement hydration reactions, leading to a lower generation of C-S-H gel and decreased strength. C4 exhibits higher strength due to its higher content of C-S-H gel and more complete hydration reaction, whereas C9, influenced by additives (PAM and sodium bentonite) [22] , manifests lower C-S-H gel content and reduced strength. This conclusion is supported by the difference in diffraction peak intensities between C4 and C9 in the XRD spectrum. Comparing C9 to sample C4, the latter exhibits distinct diffraction peaks at low angles (10°-30°), primarily composed of quartz (Qtz), albite (Ab), montmorillonite (Mrg), and C-S-H gel. Similarly, Cd4 exhibits diffraction peaks at low angles, with intensities comparable to C4, thereby indicating the presence of quartz (Qtz), albite (Ab), montmorillonite (Mrg), and C-S-H gel. The XRD spectra of C4 and Cd4 manifest similar levels of C-S-H gel content, thus indicating that both have undergone relatively complete cement hydration reactions. C-S-H gel significantly contributes to cement strength, and its sufficient generation enhances the strength of both samples. Despite the addition of PAM in Cd4, the XRD spectrum indicates that these additives did not significantly impact the cement-hydration reaction [23] , thus, the resultant material exhibits a strength approximating that of C4. The XRD spectra of C4 and Cd4 exhibit comparable levels of C-S-H gel content and strength, thus indicating similar degrees of cement hydration reaction and adequate C-S-H gel formation. This conclusion is validated by the similarity in diffraction peak intensities between C4 and Cd4 in the XRD spectrum. C4 exhibits a prominent peak at approximately 2θ = 26°, which is characteristic of quartz (Qtz). Other significant peaks appear at values approximating 2θ = 28°, 35°, and 50°, corresponding to C-S-H gel (calcium silicate hydrate), sodium zeolite (Ab), and calcite (Cal), respectively. Cd8 also exhibits a quartz (Qtz) peak approximating 2θ = 26°, albeit with lower intensity compared to C4. Significant peaks are observed at 2θ = 21°, 29°, 33°, 36°, and 49°, corresponding to sodium zeolite (Ab), montmorillonite (Mrg), and calcium montmorillonite (Cam). C4 contains a higher content of C-S-H gel (4-C-S-H gel), which is the primary cementitious material formed during cement hydration and contributes to its high strength. Although Cd8 also contains C-S-H gel, its content is noticeably lower, and it includes a higher proportion of sodium bentonite (calcium montmorillonite), i.e., relatively soft minerals [24] , thereby contributing less to strength. The C4 XRD pattern exhibits higher crystallinity with sharp, intense peaks, indicating a dense and compact structure, which potentially rationalizes its high strength. By contrast, Cd8 exhibits broader and lower-intensity peaks for various minerals, indicating lower crystallinity and a less compact structure compared to C4. In summary, the higher strength of C4 is primarily attributable to its higher C-S-H gel content, more optimal crystallinity, and compact structure. Although Cd8 contains C-S-H gel, the sample exhibits lower strength due to the inclusion of sodium bentonite and lower crystallinity. 3.2 SEM Experiment To further investigate the strength mechanisms of cement-stabilized pipe-jacking waste soil , SEM experiments were conducted on samples C4, C9, Cd4, and Cd8. From Figure 14, it can be observed that C4 exhibits a dense microstructure with low porosity. A substantial amount of uniformly distributed hydration products, such as C-S-H gel, fill the pores. This dense structure provides high strength, which is attributed to the high content of C-S-H gel and compact microstructure. Cd4 exhibits a relatively compact microstructure but with slightly higher porosity compared to C4. Although hydration products are relatively evenly distributed, larger pores are manifested in some areas. Despite a higher content of C-S-H gel in Cd4, its strength is lower than that of C4 due to the slightly higher porosity. In the C9 microstructure, more pores are visible with the uneven distribution of hydration products, and some particles appear partially unreacted. C9 exhibits higher porosity, uneven distribution of hydration products, and potentially unreacted sodium bentonite particles, leading to lower strength compared to Cd4. The microstructure of Cd8 samples reveals significant pores and cracks, a low content and uneven distribution of hydration products, and a loose structure. The high porosity and cracks, along with the uneven distribution of hydration products, and the incorporation of sodium bentonite further reduce the overall strength of Cd8, making it the weakest sample. 3.3 IR Analysis For a deeper exploration of the chemical changes in solidified waste soil , infrared spectroscopy analysis was conducted. Figure 15 indicates that the Si-O vibration peak of C4 is the strongest, thus indicating the highest C-S-H gel content, which is the most significant contributor to strength in cement hydration products. The remaining samples are ranked as follows in order of decreasing strength decreasing: Cd4, C9, and Cd8. The intensity of the O-H vibration peak reflects the quantity of hydration products. The higher intensity of the O-H vibration peaks in C4 and Cd4 indicates a greater amount of hydration products, which enhances the material's strength. Contrastingly, the weaker O-H vibration peaks in C9 and Cd8 are indicative of fewer hydration products, thereby impacting the material's strength. Cd8 and C9 contain sodium bentonite, which (although improving certain properties of the solidified products) reduces strength at higher concentrations due to its inherently lower strength and potential interference with cement-hydration reactions. In summary, the high strength of C4 is primarily attributed to its high C-S-H gel content and extensive hydration products, whereas the low strength of Cd8 is attributable to its lower C-S-H gel content, fewer hydration products, and to the presence of sodium bentonite weakening the overall strength. Cd4 and C9 exhibit strengths between these extremes, C9's lower sodium bentonite concentration and Cd4's contribution of strength from PAM lie between the two. 4. Conclusions (1) The results of the unconfined compressive strength tests revealed that utilizing a 9% cement concentration exerts a significant solidification effect on cement-stabilized pipe-jacking waste soil. At a the aforementioned cement concentration, the 7-day strength of the stabilized soil exceeded 1 MPa, meeting the requirements for road subbase materials. Under unchanged conditions, as the cement content increased to 9%, the 28-day strength of the stabilized soil attained 1.59 MPa (for original muck without PAM and Na-Ben) and 1.36 MPa (for pipe-jacking waste soil with added PAM and Na-Ben), thus indicating a slightly lower strength for the muck stabilized after modification with PAM and Na-Ben compared to the original stabilized waste soil. (2) Dry–wet cycling and freeze–thaw cycling experiments revealed that cement-stabilized pipe-jacking waste soil, within the analyzed ratios, exhibited slightly higher mass and strength-loss rates after dry–wet and freeze–thaw cycles compared to undisturbed soil. This observation indicates that the modified muck, which initially exhibited superior workability, exhibited poorer performance upon solidification. (3) Based on XRD, SEM, and IR tests combined with compressive strength results, it was observed that in the cement solidification system, when the PAM concentration was below 0.8%, the addition of PAM solution exerted a minimal and consistent impact on the strength of the solidified soil. This observation can primarily be rationalized as follows: while the PAM solution absorbs moisture and affects hydration, lower concentrations can form polyacrylamide gel, thereby promoting a tighter bond with mineral particles. In the cement solidification system, the concentration of sodium bentonite induced a strength-reduction effect. This observation can be explained as follows: sodium bentonite absorbs moisture, affects cement hydration, and accumulates to form pores in the cement solidification system, leading to an uneven internal structure, generating more pores, and inhibiting the formation of cementitious products. 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A., Hamdan, E. H., Gharaibeh, M. A., & Hanandeh, A. E. (2021). Improving aggregate stability and hydraulic properties of Sandy loam soil by applying polyacrylamide polymer. Soil and Tillage Research, 206. https://doi.org/10.1016/j.still.2020.104821Wersin P,Curti E,Appelo C A J.Modelling bentonite-water interactions at high solid/liquid ratios:swelling and diffuse double layer effects .Applied Clay Science,2004,26:249－257. Xue, Y., Gao, M., Yuan, F., & Li, H. (2021). Effect of polyacrylamide on early strength and failure form of lime stabilized soil. Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica, 38(4), 1283–1291. https://doi.org/10.13801/j.cnki.fhclxb.20200730.002 Zhang, T., Deng, Y., Lan, H., Zhang, F., Zhang, H., Wang, C., Tan, Y., & Yu, R. (2019). Experimental investigation of the compactability and cracking behavior of polyacrylamide-treated saline soil in Gansu Province, China. Polymers, 11(1). https://doi.org/10.3390/polym11010090 Hu, P., & Yang, Q. (2012). Experimental study of swelling characteristics of bentonite-sand mixture. Yantu Lixue/Rock and Soil Mechanics, 33(2), 453–458. Wang, L., Chen, X., Su, D., Zhou, W., Sun, B., Pan, J., Wu, Y., & Feng, M. (2024). Construction of a super-large prefabricated rectangular tunnel beneath a box culvert using pipe jacking: A case study. Tunnelling and Underground Space Technology, 152. https://doi-org.ntust.sjlib.cn/10.1016/j.tust.2024.105913 Additional Declarations No competing interests reported. Supplementary Files Rawdate.zip Cite Share Download PDF Status: Posted Version 1 posted 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-4728114","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":335413098,"identity":"0d771d6f-7e01-44df-9f78-753ae8cccf29","order_by":0,"name":"Xu Youjun","email":"","orcid":"","institution":"Inner Mongolia University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Xu","middleName":"","lastName":"Youjun","suffix":""},{"id":335413099,"identity":"c4bc33e0-0b55-463a-bedf-cca7cb9d0699","order_by":1,"name":"Li Zhenyu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0klEQVRIiWNgGAWjYDACCcbGAwwMFgwM7I2NDz8QqaUBqEWCgYHncLOxBHFaGBggWiTS2wR4iNHBP7u54cCHCgl7g5sP24A67eR0GwhZcudgw8EZZySYDW4ntj0oYEg2NjtAyJobiQ2Hedsk2IBa2g0kGA4kbiOkRR6k5e8/CR6DmwfbJHiI0WIA0sLYICFhcIORSC2GIL/0HJMwkDyTCAxkAyL8Ine7/eGDHzU29nzHjz98+KHCTo6w92FAAazSgFjlICDfQIrqUTAKRsEoGFEAAA2rSWdcY7+7AAAAAElFTkSuQmCC","orcid":"","institution":"Inner Mongolia University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Li","middleName":"","lastName":"Zhenyu","suffix":""},{"id":335413100,"identity":"6f6d7e86-edc2-42c2-9cb3-bb258f0ddf5a","order_by":2,"name":"Chen Zhigang","email":"","orcid":"","institution":"China Second Metallurgy Group Corporation 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Strength\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/23ff78a501005b5a239d64e0.png"},{"id":61872054,"identity":"92001c15-4bcd-47e1-a2dc-8b6f39774d3d","added_by":"auto","created_at":"2024-08-06 13:22:52","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":185433,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between Unconfined Compressive Strength and PAM Solution Concentration\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/972213f22cdee9a4dfaf1f6c.png"},{"id":61871496,"identity":"5eb8184b-13da-4547-9ca2-7bb108c6e5ba","added_by":"auto","created_at":"2024-08-06 13:14:52","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":118868,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between Unconfined Compressive Strength and the Concentration of the Sodium-based Bentonite Solution\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/ce6dcf0c0afa36112f2c96e5.png"},{"id":61872663,"identity":"4636fe17-1350-4d09-93ad-22a03e7ab06e","added_by":"auto","created_at":"2024-08-06 13:30:52","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":412726,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eApparent state of specimens under the action of wet–dry cycles\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/c5386eba9a0bc98f4b7e2d83.png"},{"id":61870362,"identity":"413d2019-1d2d-483f-8f63-653bac7de578","added_by":"auto","created_at":"2024-08-06 12:58:52","extension":"png","order_by":8,"title":"Figure 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Conditions\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/08db366fe3ba9343beaa2ea1.png"},{"id":61870370,"identity":"4782c059-0ea5-42bd-ad00-0f7dc749a706","added_by":"auto","created_at":"2024-08-06 12:58:52","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":411379,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eApparent state of specimens under the action of freeze–thaw cycles\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/ca3deaad4048457973a014b2.png"},{"id":61872666,"identity":"1e03c483-2807-49d2-9f4f-0e7dcc8f0752","added_by":"auto","created_at":"2024-08-06 13:30:52","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":96833,"visible":true,"origin":"","legend":"\u003cp\u003eThe relationship between sample strength and number of cycles under freeze–thaw cycling conditions.\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/eac1829b1f205aca8f3caa0a.png"},{"id":61870928,"identity":"90ce6641-671e-4421-aedd-4b6b991c3223","added_by":"auto","created_at":"2024-08-06 13:06:52","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":106511,"visible":true,"origin":"","legend":"\u003cp\u003eThe relationship between mass-loss rate and number of cycles under freeze–thaw cycling conditions\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/0a9406e4db853abea2ada0f7.png"},{"id":61872057,"identity":"477b86ea-ad4d-42e8-8dff-6c22a8f9c088","added_by":"auto","created_at":"2024-08-06 13:22:52","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":168884,"visible":true,"origin":"","legend":"\u003cp\u003eX-ray Diffraction（XRD）\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/6d9e3d24f65a4eb41dcdb899.png"},{"id":61870375,"identity":"9e8eccd6-15f7-4eee-a2f0-c586ce0f6ab1","added_by":"auto","created_at":"2024-08-06 12:58:52","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":788863,"visible":true,"origin":"","legend":"\u003cp\u003eScanning Electron Microscope (SEM)\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/1daebf55d661762ba64c0078.png"},{"id":61872670,"identity":"16df4c55-b75c-4980-8399-ac98da8cd93e","added_by":"auto","created_at":"2024-08-06 13:30:53","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":102886,"visible":true,"origin":"","legend":"\u003cp\u003eInfrared Spectroscopy Analysis\u003c/p\u003e","description":"","filename":"15.png","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/be80a1a15f3262f571f0778e.png"},{"id":84047558,"identity":"abfe1bf0-3954-4d82-a40b-0bdd1cd59e43","added_by":"auto","created_at":"2025-06-06 07:47:19","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4516124,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/0730c2bc-5b6e-453f-a29b-4a8efcf1ee4b.pdf"},{"id":61870366,"identity":"cedaf410-d2b1-4498-bd2e-ab8dcc682640","added_by":"auto","created_at":"2024-08-06 12:58:52","extension":"zip","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":936983,"visible":true,"origin":"","legend":"","description":"","filename":"Rawdate.zip","url":"https://assets-eu.researchsquare.com/files/rs-4728114/v1/6ee44b11670d8c914b2db8d4.zip"}],"financialInterests":"No competing interests reported.","formattedTitle":"Performance Analysis of Pipe-Jacking Waste Soils Solidified with Cement under Balanced Earth Pressure Conditions","fulltext":[{"header":"0. Introduction","content":"\u003cp\u003eThe pipe-jacking machine features precise control over direction and depth, maintains geological stability, minimizes surface disruption, and facilitates efficient construction, thereby providing crucial support for modern tunneling and pipeline installation\u0026nbsp;\u003csup\u003e[25]\u003c/sup\u003e. However, ensuring controlled chamber pressure and the smooth discharge of pipe-jacking waste soil often requires the addition of various polymer materials, thus, the original soil can be enhanced to an ideal flowable state\u0026nbsp;\u003csup\u003e[1]\u003c/sup\u003e. With the increasing implementation of pipe-jacking projects, corresponding environmental issues have emerged. The efficient utilization and treatment of muck after the addition of polymer modifiers have gradually attracted the attention of both academia and the engineering community.\u003c/p\u003e\n\u003cp\u003eTraditionally, waste soil is typically disposed of by stacking or landfilling in abandoned mines\u0026nbsp;\u003csup\u003e[2]\u003c/sup\u003e. Due to the incorporation of certain amounts of mineral-based bentonite and PAM materials, the muck forms a \u0026quot;plastic flow state,\u0026quot; leading to reduced stacking heights and significantly increased land occupation. Waste soil generated from pipe jacking faces challenges in storage, handling, and utilization, with improper disposal methods potentially leading to ecological environmental pollution.\u003c/p\u003e\n\u003cp\u003eCement, a crucial building material, offers multiple advantages such as high strength, durability, resistance to pressure, and natural erosion. The material is cost-effective, easy to work with, and widely utilized in various construction and infrastructure projects.\u003c/p\u003e\n\u003cp\u003eResearchers (both domestically and internationally) have explored the incorporation of cement into soil for resource utilization. For instance, Rui et al. \u003csup\u003e[3]\u003c/sup\u003e prepared a Controlled Low Strength Material (CLSM) by mixing muck with water, cement, fine sand, and fly ash in specific proportions, which can replace some conventional backfill materials. Wei et al. \u003csup\u003e[4]\u003c/sup\u003e investigated the blend of nanosilica with cementitious soil, thus demonstrating the favorable dynamic properties of this composite material. Jing et al. \u003csup\u003e[5]\u003c/sup\u003e combined Pisha sandstone with cement to create fill materials, effectively addressing soil management issues in their region. Zhang et al. \u003csup\u003e[6]\u0026nbsp;\u003c/sup\u003eutilized recycled phosphogypsum and calcium aluminate cement, by mixing these materials with dredged soil, they obtained soil with enhanced properties after solidification. This material offers significant environmental sustainability, economic benefits, and engineering value. Ayawanna et al. \u003csup\u003e[7]\u003c/sup\u003e created a material by mixing steel slag, cement, and soil that exceeded standard acceptable values (0.6 MPa). Li et al. \u003csup\u003e[8]\u003c/sup\u003e mixed groove-cut soil with residues from calcination and fiber blended cement, which exhibited satisfactory performance.\u003c/p\u003e\n\u003cp\u003eIn summary, particularly for soil stabilization applications, cement exhibits potential effectiveness. However, pipe-jacking soil contains components such as polyacrylamide (PAM) and sodium bentonite (Na-Ben), which differ significantly in chemical composition from undisturbed soil. Currently, there is limited research on the applicability and effectiveness of cement-based stabilization methods specifically tailored for pipe-jacking waste soil.\u003c/p\u003e\n\u003cp\u003eTherefore, this study proposes the utilization of cement for the solidification treatment of pipe-jacking muck. The researchers aim to investigate various factors influencing the solidification strength, analyze the microstructure of the solidified pipe-jacking soil, and study its resistance to freeze\u0026ndash;thaw cycles and wet\u0026ndash;dry durability. The anticipated research outcomes aim to provide scientific justification and technical guidance for the resource utilization of pipe-jacking soil as road base material, thereby promoting its practical application.\u003c/p\u003e"},{"header":"1. Experimental Materials and Methods","content":"\u003ch2\u003e1.1 Experimental Objective\u003c/h2\u003e\n\u003cp\u003eAccording to the \u0026quot;Technical Code for Highway Pavement Base Construction JTG/T F20-2015\u0026quot; specifications, this study conducts indoor experiments to investigate the unconfined compressive strength, freeze\u0026ndash;thaw durability, and wet\u0026ndash;dry durability of cement-stabilized pipe-jacking muck. The research aims to reveal the microstructure of the stabilized waste soil and propose cementitious mix designs that meet the requirements for the road base materials specified in the code. This endeavor seeks to provide a foundation for the application of pipe-jacking waste soil in road subbase layers, thus promoting sustainable practices in civil engineering projects.\u003c/p\u003e\n\u003ch2\u003e1.2 Experimental Materials\u003c/h2\u003e\n\u003cp\u003eThe experimental soil is the original, unimproved pipe-jacking soil excavated during the introduction of reclaimed water in a metal deep processing industrial park in a certain city. The original appearance of the pipe-jacking soil is depicted in Figure 1. The soil type is fine sand, and the particle size distribution curve is depicted in Figure 2.\u003c/p\u003e\n\u003cp\u003eThe strata encountered during pipe jacking primarily comprises silty sand, with its physical and mechanical parameters detailed in Table 1. This type of stratum is characterized by low cohesive strength, a poor arching effect, and short self-stabilization time, which necessitates the addition of materials such as PAM solution and sodium-based bentonite to enhance the original slag soil to an ideal flowable state \u003csup\u003e[9]\u003c/sup\u003e, providing a crucial prerequisite for the smooth advancement of pipe-jacking operations.\u003c/p\u003e\n\u003cp\u003eTable 1 Basic physical parameters of pipe-jacking residue\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eDeformation modulus/（Mpa）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eInternal friction angle/（\u0026deg;）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eCohesion/（Kpa）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eNatural density/（KN/m\u003csup\u003e3\u003c/sup\u003e）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eWater content/%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e19.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e6.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThis study proposes the utilization of cement for the solidification of the enhanced pipe-jacking waste soil. The main components of the enhanced material and the solidification material identified through X-ray fluorescence spectroscopy (XRF) are listed in Table 2.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 2 Main chemical composition of test raw materials\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.666666666666668%\" rowspan=\"2\"\u003e\n \u003cp\u003eRaw materials\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"83.33333333333333%\" colspan=\"9\"\u003e\n \u003cp\u003eContent of each component in the raw materials/%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.746812386156648%\"\u003e\n \u003cp\u003eMgO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.021857923497267%\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.021857923497267%\"\u003e\n \u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.746812386156648%\"\u003e\n \u003cp\u003eSO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.746812386156648%\"\u003e\n \u003cp\u003eNa\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.564663023679417%\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.021857923497267%\"\u003e\n \u003cp\u003eCaO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.564663023679417%\"\u003e\n \u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.564663023679417%\"\u003e\n \u003cp\u003eCl\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.69195751138088%\" valign=\"top\"\u003e\n \u003cp\u003eCement\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.952959028831563%\"\u003e\n \u003cp\u003e1.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.015174506828528%\"\u003e\n \u003cp\u003e7.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.015174506828528%\"\u003e\n \u003cp\u003e22.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.952959028831563%\"\u003e\n \u003cp\u003e3.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.952959028831563%\"\u003e\n \u003cp\u003e0.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.801213960546283%\"\u003e\n \u003cp\u003e0.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.015174506828528%\"\u003e\n \u003cp\u003e57.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.801213960546283%\"\u003e\n \u003cp\u003e0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.801213960546283%\"\u003e\n \u003cp\u003e0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.69195751138088%\" valign=\"top\"\u003e\n \u003cp\u003ePipe jacking spoil\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.952959028831563%\"\u003e\n \u003cp\u003e2.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.015174506828528%\"\u003e\n \u003cp\u003e13.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.015174506828528%\"\u003e\n \u003cp\u003e63.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.952959028831563%\"\u003e\n \u003cp\u003e0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.952959028831563%\"\u003e\n \u003cp\u003e1.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.801213960546283%\"\u003e\n \u003cp\u003e2.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.015174506828528%\"\u003e\n \u003cp\u003e8.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.801213960546283%\"\u003e\n \u003cp\u003e0.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.801213960546283%\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.69195751138088%\" valign=\"top\"\u003e\n \u003cp\u003eSodium-based bentonite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.952959028831563%\"\u003e\n \u003cp\u003e2.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.015174506828528%\"\u003e\n \u003cp\u003e16.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.015174506828528%\"\u003e\n \u003cp\u003e67.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.952959028831563%\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.952959028831563%\"\u003e\n \u003cp\u003e0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.801213960546283%\"\u003e\n \u003cp\u003e4.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.015174506828528%\"\u003e\n \u003cp\u003e2.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.801213960546283%\"\u003e\n \u003cp\u003e0.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.801213960546283%\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch2\u003e1.3 Experimental Procedure\u003c/h2\u003e\n\u003cp\u003eThe experimental procedure is illustrated in Figure 3.\u003c/p\u003e\n\u003ch2\u003e1.4 Determination of Mix Proportions\u003c/h2\u003e\n\u003cp\u003eAccording to reference\u003csup\u003e[9]\u003c/sup\u003e, a 0.2% concentration of PAM solution and a 9% concentration of sodium-based bentonite solution have exhibited satisfactory enhancement effects on pipe-jacking waste soil. Therefore, this study employs the same concentrations of additives as those listed in the reference, with 7% and 12% addition rates. At these concentrations, the modified slag soil exhibits a 169 cm slump value, thus demonstrating satisfactory workability\u003csup\u003e[10]\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eA total of 10 test conditions were designed, as illustrated in Table 3.\u003c/p\u003e\n\u003cp\u003eTable 3 Agent ratio\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"550\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eExperiment ID\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003eVolume of cement added/%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003eVolume of PAM solution added/%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003eVolume of Na-Ben\u003c/p\u003e\n \u003cp\u003esolution added/%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003eAmount of water added/%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eC1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eC2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eC3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eC4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eC5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eC6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eC7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eC8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eC9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003eC10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTo investigate the effects of PAM and sodium-based bentonite on cement solidification, the concentration of the original slag-soil improver solutions was varied under unchanged conditions, and a total of eight sets of experimental samples were designed as illustrated in Table 4.\u003c/p\u003e\n\u003cp\u003eTable 4 Concentration ratio for the modifying solution\u003c/p\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"529\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eExperiment ID\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eVolume of cement added/%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eConcentration of PAM solution/%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eConcentration of Na-Ben solution/%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003eCd1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003eCd2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003eCd3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003eCd4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003eCd5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003eCd6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003eCd7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003eCd8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\" valign=\"top\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003ch2\u003e1.5 Preparation and Curing of Specimens\u003c/h2\u003e\n\u003cp\u003eFollowing the \u0026quot;Test Code for Stabilized Materials of Highway Engineering Inorganic Binders\u0026quot; (JTG E51-2009), cylindrical specimens with dimensions of 150mm \u0026times; 150mm \u0026times; 150mm were prepared by casting, and indoor tests including compressive strength, freeze\u0026ndash;thaw cycle, and dry\u0026ndash;wet cycle were conducted.\u003c/p\u003e\n\u003ch2\u003e1.6 Experimental Parameters\u003c/h2\u003e\n\u003cp\u003eThe 7-day Unconfined Compressive Strength Requirements for Cementitious Road Base and Subbase Materials are detailed in tables 5 and 6 of the specifications.\u003c/p\u003e\n\u003cp\u003eTable 5 Requirements of compressive strength for different grades of road subgrade\u003c/p\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eHighway grade\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eExceedingly heavy traffic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eHeavy traffic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eLight traffic\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eExpressways and Class I highways\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e4.0-5.0MPa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e3.5-4.5Mpa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e3.0-4.0Mpa\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eSecondary and lower-level roads\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e3.5-4.5MPa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e3.0-4.0Mpa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e2.5-3.5Mpa\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eTable 6 Requirements of compressive strength for the subbase of different grades of roads\u003c/p\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eHighway grade\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eExceedingly heavy traffic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eHeavy traffic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eLight traffic\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eExpressways and Class I highways\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e2.5-3.5Mpa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e2.0-3.0Mpa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e1.5-2.5Mpa\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eSecondary and lower-level roads\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e2.0-3.0Mpa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e1.5-2.5Mpa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e1.0-2.0Mpa\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e"},{"header":"2. Indoor Experimental Research on Solidified Pipe-Jacking Waste Soils","content":"\u003ch2\u003e2.1 Analyzing Unconfined Compressive Strength\u003c/h2\u003e\n\u003cp\u003eTo explore the influence of stabilizing agents on the unconfined compressive strength (UCS) of stabilized pipe-jacking waste soil, unconfined compressive strength tests were conducted under varying proportions of different stabilizing agents and stabilizing agent ratios.\u003c/p\u003e\n\u003cp\u003eBased on Figure 4, under fixed ratios of sodium-based bentonite (Na-Ben) solution and polyacrylamide (PAM) solution, and with other conditions unchanged, increasing cement content leads to a moderate increase in the unconfined compressive strength (UCS) of cement-stabilized soil. However, within the analyzed ratio range, adding PAM solution and sodium-based bentonite (Na-Ben) leads to a decrease in the strength of cement-stabilized soil. The specific reasons are analyzed as follows:\u003c/p\u003e\n\u003cp\u003eImpact of PAM: PAM, a high molecular weight polymer, exhibits strong water-absorption capabilities \u003csup\u003e[11]\u003c/sup\u003e. Within the studied ratio range, the polymer absorbs moisture, reducing the available water for cement-hydration reactions, thereby limiting hydration and reducing strength.\u003c/p\u003e\n\u003cp\u003eImpact of sodium-based bentonite (Na-Ben): sodium-based bentonite (Na-Ben) is a clay mineral with significant water-absorbing and swelling capacities. Within the studied ratio range, its water-absorbing and swelling properties reduce the available moisture for cement-hydration reactions \u003csup\u003e[12]\u003c/sup\u003e, thus affecting the hydration process and structural formation of cementitious slurry, which leads to reduced strength.\u003c/p\u003e\n\u003cp\u003eChanges in pore structure: The addition of PAM and sodium-based bentonite (Na-Ben) alters the pore structure of the cementitious slurry. The particles of sodium-based bentonite (Na-Ben) and molecules of PAM form larger pores or micro-cracks within the slurry \u003csup\u003e[12]\u003c/sup\u003e, weakening the overall structure of cement, thus reducing the material\u0026rsquo;s strength.\u003c/p\u003e\n\u003cp\u003eDespite the reduction in strength due to the addition of PAM and sodium-based bentonite (Na-Ben), samples C5 and C10 still meet the strength requirements for sub-base materials of secondary highway pavements.\u003c/p\u003e\n\u003cp\u003eBased on Figure 5, under constant cement ratios, the unconfined compressive strength of stabilized slag soil at 7 days and 28 days remains nearly consistent with increasing PAM solution concentrations. Therefore, the effect of PAM solution on cement stabilization is minimal, which can primarily be explained as follows: within the studied ratio range, polyacrylamide (PAM) does not promote the formation of hydration products and only mildly affects cement hydration due to its water-absorbing properties. However, it forms a viscous gel-like substance in water, which provides certain viscosity and adhesion \u003csup\u003e[11]\u003c/sup\u003e, thereby contributing to a modest increase in strength. Consequently, the material undergoes no significant macroscopic changes in strength.\u003c/p\u003e\n\u003cp\u003eAccording to Figure 6, under constant proportions of the stabilizer, the unconfined compressive strength initially increases and subsequently decreases with increasing sodium-based bentonite concentration. This trend is primarily attributed to the characteristics of sodium-based bentonite, which, at lower concentrations, absorbs less water and fills some voids within the specimens, thereby enhancing their density and compressive strength. Additionally, after absorbing water, sodium-based bentonite forms colloids that possess adsorption capabilities \u003csup\u003e[12]\u003c/sup\u003e, thus stabilizing the structure by filling remaining voids post-cement hydration \u003csup\u003e[13]\u003c/sup\u003e. However, at higher concentrations, sodium-based bentonite induces uneven particle packing and the formation of more micro-pores within the specimens, thus reducing their density and strength \u003csup\u003e[14]\u003c/sup\u003e. Moreover, high concentrations of sodium-based bentonite absorb excessive moisture, leading to incomplete or less favorable cement hydration reactions, thereby impacting the formation of hydration products and subsequently affecting the specimens\u0026rsquo; strength.\u003c/p\u003e\n\u003ch2\u003e2.2 Analyzing Wet\u0026ndash;Dry Cycling\u003c/h2\u003e\n\u003cp\u003eTo investigate the impact of wet\u0026ndash;dry cycles on the stabilized soil, dry\u0026ndash;wet cycle tests were conducted using mixtures C4 and C9 and selected based on unconfined compressive strength experiments. CFM1 denotes the dry\u0026ndash;wet cycle specimens for mixture C4, whereas CFM2 represents those for mixture C9.\u003c/p\u003e\n\u003cp\u003eBased on Figure 8 and Figure7, the mass-loss rate gradually increases with the number of cycles. During the cycles, significant mass loss occurs, and an observation of the samples reveals that the top and bottom layers begin to spall after immersion, leading to considerable height reduction.\u003c/p\u003e\n\u003cp\u003eCombining Figure 9 with Figure 4, it is evident that the compressive strength of the 28-day samples decreases as the number of cycles increases\u003csup\u003e[15]\u003c/sup\u003e, which is primarily occasioned by the influence of the wet\u0026ndash;dry cycles on the hydration products in cement. Compounds such as ettringite and calcium aluminate hydrates, formed during cement hydration, undergo dissolution and precipitation cycles in the wet\u0026ndash;dry process, gradually loosening the material\u0026rsquo;s structure and reducing its strength\u003csup\u003e[16]\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eThe resistance to wet\u0026ndash;dry cycles is superior in sample CFM1 (mix C4) compared to CFM2 (mix C9). Although the polyacrylamide gel enhances the density and strength of CFM2 samples, during cement curing, the addition of PAM and sodium bentonite within the mixing range absorbs more moisture\u003csup\u003e[17]\u003c/sup\u003e. Moreover, sodium bentonite, within the mixing range, creates pores that affect strength formation. Therefore, CFM1 samples demonstrate more optimal performance in wet\u0026ndash;dry cycle resistance.\u003c/p\u003e\n\u003cp\u003eFrom the wet\u0026ndash;dry cycle experiments, it is evident that the cement-stabilized slag exhibits slightly reduced resistance to wet\u0026ndash;dry cycles compared to unstabilized slag within the mixing range.\u003c/p\u003e\n\u003ch2\u003e2.3 Analyzing Freeze\u0026ndash;Thaw Cycling\u003c/h2\u003e\n\u003cp\u003eBased on the compressive strength tests, CFM1 (representing mix C4) and CFM2 (representing mix C9) were selected for freeze\u0026ndash;thaw cycle experiments.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFigure 10 indicates that during the cycling process, CFM2 samples exhibited surface cracking and initial spalling. With increasing freeze\u0026ndash;thaw cycles, the spalling increased gradually, eventually leading to substantial fragment detachment, making it difficult to maintain overall integrity. Contrastingly, CFM1 samples also experienced cracks and spalling, however, the detachment of small fragments was minimal, which enabled the overall shape to remain relatively intact. This difference is primarily attributed to the addition of PAM and sodium bentonite solutions in the CFM2 samples, which reduced the overall strength and diminished their resistance to freeze\u0026ndash;thaw cycles.\u003c/p\u003e\n\u003cp\u003eBased on Figure 11, it can be observed that the strength of mixes C4 and C9 decreases with an increase in freeze\u0026ndash;thaw cycles at the age of 28 days. Sample C4 exhibits slightly more optimal freeze\u0026ndash;thaw performance compared to C9, which is primarily explained as follows: when the moisture in cement freezes, it expands to occupy a region approximating its volume, exerting significant internal pressure within the concrete, thus leading to the formation or expansion of cracks. With repeated freeze\u0026ndash;thaw cycles, these cracks multiply and expand, leading to structural damage and strength reduction. Within the specified range of ratios, the addition of PAM and sodium bentonite solutions during cement curing affects the hydration reaction of cement, with sodium bentonite increasing the number of cement structure cracks, leading to lower strength compared to specimens without added PAM.\u003c/p\u003e\n\u003cp\u003eFigure 12 indicates that as the number of cycles increases, the mass loss gradually increases. This observation is mainly attributable to the freeze\u0026ndash;thaw cycles that damage the microstructure of the concrete, thereby altering the structure of hydration products (such as ettringite and calcium hydroxide) in the cement paste, which further reduces its bonding capacity and overall strength. Additionally, freezing and thawing alter the in-concrete chemical environment \u003csup\u003e[18]\u003c/sup\u003e. For instance, during freezing, moisture from the cement paste is expelled from capillaries and re-enters during thawing, thus disrupting the cement hydration reaction through repeated processes.\u003csup\u003e[19]\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eFrom the freeze\u0026ndash;thaw cycle experiments, it is evident that the frost resistance performance of cement-stabilized modified muck within the specified ratios is lower compared to the requirements of road-base materials.\u003c/p\u003e"},{"header":"3. Studying Microstructural Characteristics of Solidified Pipe-Jacking Waste Soils","content":"\u003ch2\u003e3.1 XRD\u0026nbsp;Experiment\u003c/h2\u003e\n\u003cp\u003eTo further investigate the effect of additives in cement-stabilized pipe-jacking waste soil on the properties of stabilized muck, X-ray diffraction (XRD) experiments were conducted to analyze the mineral composition of stabilized muck.\u003c/p\u003e\n\u003cp\u003eFrom Figure 13, it is evident that compared to sample C1, sample C4 exhibits prominent diffraction peaks at low angles (10\u0026deg;-30\u0026deg;), mainly composed of quartz (Qtz), albite (Ab), montmorillonite (Mrg), and C-S-H gel. Similarly, sample C9 also illustrates diffraction peaks at low angles, albeit with lower intensity, which indicates the presence of quartz (Qtz), albite (Ab), montmorillonite (Mrg), and C-S-H gel. Due to the addition of PAM and sodium bentonite in C9, these additives influence the cement hydration process, leading to a reduced generation of C-S-H gel. The XRD spectrum of C4 demonstrates a higher content of C-S-H gel, indicating a more thorough cement-hydration reaction. C-S-H gel is a primary contributor to cement strength, and its higher content directly enhances the sample\u0026apos;s strength. Contrastingly, C9, due to the inclusion of PAM and sodium bentonite \u003csup\u003e[20-21]\u003c/sup\u003e, may adversely affect cement hydration reactions, leading to a lower generation of C-S-H gel and decreased strength. C4 exhibits higher strength due to its higher content of C-S-H gel and more complete hydration reaction, whereas C9, influenced by additives (PAM and sodium bentonite)\u003csup\u003e\u0026nbsp;[22]\u003c/sup\u003e, manifests lower C-S-H gel content and reduced strength. This conclusion is supported by the difference in diffraction peak intensities between C4 and C9 in the XRD spectrum.\u003c/p\u003e\n\u003cp\u003eComparing C9 to sample C4, the latter exhibits distinct diffraction peaks at low angles (10\u0026deg;-30\u0026deg;), primarily composed of quartz (Qtz), albite (Ab), montmorillonite (Mrg), and C-S-H gel. Similarly, Cd4 exhibits diffraction peaks at low angles, with intensities comparable to C4, thereby indicating the presence of quartz (Qtz), albite (Ab), montmorillonite (Mrg), and C-S-H gel. The XRD spectra of C4 and Cd4 manifest similar levels of C-S-H gel content, thus indicating that both have undergone relatively complete cement hydration reactions. C-S-H gel significantly contributes to cement strength, and its sufficient generation enhances the strength of both samples. Despite the addition of PAM in Cd4, the XRD spectrum indicates that these additives did not significantly impact the cement-hydration reaction \u003csup\u003e[23]\u003c/sup\u003e, thus, the resultant material exhibits a strength approximating that of C4. The XRD spectra of C4 and Cd4 exhibit comparable levels of C-S-H gel content and strength, thus indicating similar degrees of cement hydration reaction and adequate C-S-H gel formation. This conclusion is validated by the similarity in diffraction peak intensities between C4 and Cd4 in the XRD spectrum.\u003c/p\u003e\n\u003cp\u003eC4 exhibits a prominent peak at approximately 2\u0026theta; = 26\u0026deg;, which is characteristic of quartz (Qtz). Other significant peaks appear at values approximating 2\u0026theta; = 28\u0026deg;, 35\u0026deg;, and 50\u0026deg;, corresponding to C-S-H gel (calcium silicate hydrate), sodium zeolite (Ab), and calcite (Cal), respectively. Cd8 also exhibits a quartz (Qtz) peak approximating 2\u0026theta; = 26\u0026deg;, albeit with lower intensity compared to C4. Significant peaks are observed at 2\u0026theta; = 21\u0026deg;, 29\u0026deg;, 33\u0026deg;, 36\u0026deg;, and 49\u0026deg;, corresponding to sodium zeolite (Ab), montmorillonite (Mrg), and calcium montmorillonite (Cam). C4 contains a higher content of C-S-H gel (4-C-S-H gel), which is the primary cementitious material formed during cement hydration and contributes to its high strength. Although Cd8 also contains C-S-H gel, its content is noticeably lower, and it includes a higher proportion of sodium bentonite (calcium montmorillonite), i.e., relatively soft minerals\u003csup\u003e[24]\u003c/sup\u003e, thereby contributing less to strength. The C4 XRD pattern exhibits higher crystallinity with sharp, intense peaks, indicating a dense and compact structure, which potentially rationalizes its high strength. By contrast, Cd8 exhibits broader and lower-intensity peaks for various minerals, indicating lower crystallinity and a less compact structure compared to C4. In summary, the higher strength of C4 is primarily attributable to its higher C-S-H gel content, more optimal crystallinity, and compact structure. Although Cd8 contains C-S-H gel, the sample exhibits lower strength due to the inclusion of sodium bentonite and lower crystallinity.\u003c/p\u003e\n\u003ch2\u003e3.2 SEM\u0026nbsp;Experiment\u003c/h2\u003e\n\u003cp\u003e\u0026nbsp;To further investigate the strength mechanisms of cement-stabilized pipe-jacking waste soil , SEM experiments were conducted on samples C4, C9, Cd4, and Cd8.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFrom Figure 14, it can be observed that C4 exhibits a dense microstructure with low porosity. A substantial amount of uniformly distributed hydration products, such as C-S-H gel, fill the pores. This dense structure provides high strength, which is attributed to the high content of C-S-H gel and compact microstructure.\u003c/p\u003e\n\u003cp\u003eCd4 exhibits a relatively compact microstructure but with slightly higher porosity compared to C4. Although hydration products are relatively evenly distributed, larger pores are manifested in some areas. Despite a higher content of C-S-H gel in Cd4, its strength is lower than that of C4 due to the slightly higher porosity.\u003c/p\u003e\n\u003cp\u003eIn the C9 microstructure, more pores are visible with the uneven distribution of hydration products, and some particles appear partially unreacted. C9 exhibits higher porosity, uneven distribution of hydration products, and potentially unreacted sodium bentonite particles, leading to lower strength compared to Cd4.\u003c/p\u003e\n\u003cp\u003eThe microstructure of Cd8 samples reveals significant pores and cracks, a low content and uneven distribution of hydration products, and a loose structure. The high porosity and cracks, along with the uneven distribution of hydration products, and the incorporation of sodium bentonite further reduce the overall strength of Cd8, making it the weakest sample.\u003c/p\u003e\n\u003ch2\u003e3.3 IR Analysis\u003c/h2\u003e\n\u003cp\u003eFor a deeper exploration of the chemical changes in solidified waste soil , infrared spectroscopy analysis was conducted. Figure 15 indicates that the Si-O vibration peak of C4 is the strongest, thus indicating the highest C-S-H gel content, which is the most significant contributor to strength in cement hydration products. The remaining samples are ranked as follows in order of decreasing strength decreasing: Cd4, C9, and Cd8. The intensity of the O-H vibration peak reflects the quantity of hydration products. The higher intensity of the O-H vibration peaks in C4 and Cd4 indicates a greater amount of hydration products, which enhances the material\u0026apos;s strength. Contrastingly, the weaker O-H vibration peaks in C9 and Cd8 are indicative of fewer hydration products, thereby impacting the material\u0026apos;s strength. Cd8 and C9 contain sodium bentonite, which (although improving certain properties of the solidified products) reduces strength at higher concentrations due to its inherently lower strength and potential interference with cement-hydration reactions.\u003c/p\u003e\n\u003cp\u003eIn summary, the high strength of C4 is primarily attributed to its high C-S-H gel content and extensive hydration products, whereas the low strength of Cd8 is attributable to its lower C-S-H gel content, fewer hydration products, and to the presence of sodium bentonite weakening the overall strength. Cd4 and C9 exhibit strengths between these extremes, C9\u0026apos;s lower sodium bentonite concentration and Cd4\u0026apos;s contribution of strength from PAM lie between the two.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003e(1)\u0026nbsp;The results of the unconfined compressive strength tests revealed that utilizing a 9% cement concentration exerts a significant solidification effect on cement-stabilized pipe-jacking waste soil. At a the aforementioned cement concentration, the 7-day strength of the stabilized soil exceeded 1 MPa, meeting the requirements for road subbase materials. Under unchanged conditions, as the cement content increased to 9%, the 28-day strength of the stabilized soil attained 1.59 MPa (for original muck without PAM and Na-Ben) and 1.36 MPa (for pipe-jacking waste soil with added PAM and Na-Ben), thus indicating a slightly lower strength for the muck stabilized after modification with PAM and Na-Ben compared to the original stabilized waste soil.\u003c/p\u003e\n\u003cp\u003e(2)\u0026nbsp;Dry\u0026ndash;wet cycling and freeze\u0026ndash;thaw cycling experiments revealed that cement-stabilized pipe-jacking waste soil, within the analyzed ratios, exhibited slightly higher mass and strength-loss rates after dry\u0026ndash;wet and freeze\u0026ndash;thaw cycles compared to undisturbed soil. This observation indicates that the modified muck, which initially exhibited superior workability, exhibited poorer performance upon solidification.\u003c/p\u003e\n\u003cp\u003e(3) Based on XRD, SEM, and IR tests combined with compressive strength results, it was observed that in the cement solidification system, when the PAM concentration was below 0.8%, the addition of PAM solution exerted a minimal and consistent impact on the strength of the solidified soil. This observation can primarily be rationalized as follows: while the PAM solution absorbs moisture and affects hydration, lower concentrations can form polyacrylamide gel, thereby promoting a tighter bond with mineral particles. In the cement solidification system, the concentration of sodium bentonite induced a strength-reduction effect. This observation can be explained as follows: sodium bentonite absorbs moisture, affects cement hydration, and accumulates to form pores in the cement solidification system, leading to an uneven internal structure, generating more pores, and inhibiting the formation of cementitious products.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo potential conflict of interest was reported by the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statements\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe datasets used and analysed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZhang, P., Zhang, Y., Ariaratnam, S. T., Ma, B., Zeng, C., \u0026amp; Liu, K. (2023). 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Tunnelling and Underground Space Technology, 152. https://doi-org.ntust.sjlib.cn/10.1016/j.tust.2024.105913\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Pipe-jacking waste soil, Recycled solidification filling material, Mechanical properties, Microstructural test, Wet-dry test, Freeze-thaw test","lastPublishedDoi":"10.21203/rs.3.rs-4728114/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4728114/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The utilization of pipe-jacking soil poses challenges due to its complex composition, which comprises polyacrylamide (PAM) and sodium bentonite (Na-Ben) surfactants, hindering drainage and solidification. Improper handling may induce environmental pollution. To address this problem, cement solidification was explored after modification with PAM and Na-Ben. By performing indoor resistance tests, freeze–thaw cycles, wet–dry cycles, SEM, XRD, and IR experiments, it was found that within certain ratios, cement solidification effectively stabilizes pipe-jacking waste soil. Specifically, PAM minimally impacts pipe-jacking waste-soil strength, whereas Na-Ben slightly reduces it. Microscopic analysis revealed that although water absorption hinders hydration reactions, PAM (at lower concentrations) promotes mineral particle cohesion during cement solidification. Na-Ben tends to aggregate, leading to uneven internal structure and inhibiting cementitious product formation","manuscriptTitle":"Performance Analysis of Pipe-Jacking Waste Soils Solidified with Cement under Balanced Earth Pressure Conditions","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-06 12:58:47","doi":"10.21203/rs.3.rs-4728114/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e2210910-6cf3-4ae1-bc35-b81feec6e939","owner":[],"postedDate":"August 6th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":35526436,"name":"Physical sciences/Engineering/Civil engineering"},{"id":35526437,"name":"Earth and environmental sciences/Environmental sciences/Environmental chemistry"}],"tags":[],"updatedAt":"2025-06-06T07:39:07+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-06 12:58:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4728114","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4728114","identity":"rs-4728114","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}