Crack Evolution and its Quantitative Analysis on Unsaturated Loess and Paleosoil

Crack Evolution and its Quantitative Analysis on Unsaturated Loess and Paleosoil | 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 Research Article Crack Evolution and its Quantitative Analysis on Unsaturated Loess and Paleosoil Yu Xing, Tie Hang Wang, Zai Kun Zhao This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5294720/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 alternating loess and loess paleo-soil layers exhibit distinct water contraction cracking behavior in the loess region. Investigating these characteristics is essential for projects in loess areas. This study focused on Q 3 loess and loess samples, revealing the following key findings:(1) Cracking occurs in three stages: crack initiation, skeleton formation, and complete development. (2) Loess paleo-soil requires higher initial cracking water content than Q 3 loess. After crack development, the overall water content of paleosoil remains higher. (3) Cracks are wider but fewer in paleo-soil. The highest water content is at the specimen’s edge. (4) Initial water content affects crack rate ( r ), total crack length ( L ), and average crack width ( D av ) in both loess and loess paleo-soil specimens. Conversely, initial dry density inhibits r and L but promotes D av . (5) The two modes of the presence of clay grains result in higher clay content loess paleosols having greater deformability and soil tensile strength than Q 3 loess. Deformation-induced tensile forces and soil tensile strength play distinct roles during early and late crack development. (6) Using fracture toughness, energy diffusion formulas, and the elasticity model, it is concluded that paleosol has a weaker ability to produce new cracks but better deformation performance compared to Q 3 loess. loess paleosols loess crack evolution moisture content dry density Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1 Introduction Paleosols in loess regions are soil layers formed during periods of aeolian accumulation under alternating dry and wet climatic conditions. Biological growth during these periods significantly influenced soil formation, resulting in a high content of cohesive particles. These paleosols are notably prone to cracking. When exposed, they become more unstable after dehydration cracking compared to typical loess. This instability can lead to severe environmental disasters, such as weathering grooves on loess slopes and instability around tunnel entrances. Expansive soils are known for their distinct desiccation shrinkage and cracking characteristics. Most studies on desiccation cracking focus on expansive soils, using methods like CT scanning to observe internal soil fracture(Wang 2018; Huang 2021), graphic analysis software for fracture data processing(Sun 2021), fractal theory for evaluating cracking(Zhao 2022; Fu 2022; Tang 2023), and elastic mechanics theory-based models for cracking(Wu 2012; Menon 2019 ). In contrast, existing loess research predominantly investigates native cracks and changes in engineering properties resulting from factors like loading, freeze-thaw cycles, and wet-dry cycles. For instance, Li(2018) examined fracture evolution in loess under freeze-thaw and wet-dry conditions. Zhou(2018) investigated these properties in loess samples exposed to freeze-thaw cycles. Feng(2021) developed a 3D creep constitutive model for native loess within crack zones. Similarly, Xu(2023) studied engineering properties such as volume, void ratio, and collapsible settlement of loess samples subjected to freeze-thaw cycles. Additionally, Tang(2024) explored deformation characteristics, stress variations, and failure modes in loess slopes induced by loading. Significant differences in particle size distribution exist between Q 3 loess and remolded paleosol soils. Studies on the impact of clay content on soil cracking often consider factors like soil water content and dry density. For instance, Abbaszadeh(2015) investigates how different clay contents and water contents affect the development of cracks and the hydraulic properties of the soil. Li(2019) examined the influence of coarse particles on the cracking of cohesive soils. Zhong(2022) focuses on the effects of initial water content and dry density on the shrinkage and cracking behavior of compacted clay. These studies highlight the critical impact of particle size distribution on soil cracking. However, the distinctive soil composition and deformation characteristics of loess paleosols compared to other soils make it challenging to evaluate their fracture evolution characteristics. The study of fracture evolution characteristics of loess paleosols under dehydration shrinkage conditions, and their differences from Q 3 loess, is of significant importance. The authors prepared large-sized compacted samples of Q 3 loess and paleosols and conducted comparative experiments on fracture evolution under ambient drying conditions. Fracture development was recorded in real-time, and a moisture field model was established by dividing the area into grids. High-definition cameras were used to compare the fracture evolution patterns of loess and paleosols under dry conditions in detail, further exploring the underlying mechanisms. 2 Samples and Methods 2.1 Sample Preparation The Q 3 loess used in the test was sourced from a construction site in Xianyang, China, while the loess-paleosol was taken from a highway construction section in Weinan, China. Both types of test soils are widely distributed in the loess area. The physical indexes of the soils obtained from the geotechnical tests are shown in Table 1 : Table 1 Physical properties of Q3 loess and paleosol Types of loess liquid limit, w L /% plastic limit, w P /% plasticity index, I P Q 3 loess 29.4 17.6 11.8 Loess paleosol 32.6 18.8 13.8 During dehumidification, the overall shrinkage of small-sized models significantly affects size changes(2024). This shrinkage constrains the formation of surface cracks and impacts test results. The thickness of the soil layer also influences quantitative parameters such as the number of nodes and cracks in the fracture network(2020). Samples with greater thickness exhibit single, wide fractures with a pronounced boundary effect. To minimize these influences on result statistics, the test refers to the model design of Liu(2021) and uses a large-sized model with dimensions of 575mm × 380mm × 20mm, resulting in a width-thickness ratio of only 0.053. By geotechnical testing standards, soil samples were air-dried, crushed, and sieved. The required amount was weighed and mixed with deionized water to achieve a specific water content. The mixture was left to stand for 24 hours to ensure uniform moisture distribution. The soil was then placed in a mold and compacted to a thickness of 20mm. The open side was covered with cling film, which was removed after 24 hours to prepare for testing. 2.2 Experimental Scheme The experiment considers the impact of initial water content and dry density on soil cracking. The parameters are set as shown in Table 2 : Table 2 Test group parameter setting Number Types of loess Initial water content, \({w_0}\) /% Soil dry density, \({\rho _{\text{d}}}\) /g·cm − 3 A1 Q 3 loess 30 1.4 B1 loess-paleosol 30 1.4 A2 Q 3 loess 28 1.4 B2 loess-paleosol 28 1.4 A3 Q 3 loess 26 1.4 B3 loess-paleosol 26 1.4 A4 Q 3 loess 30 1.5 B4 loess-paleosol 30 1.5 A5 Q 3 loess 30 1.6 B5 loess-paleosol 30 1.6 A6 Q 3 loess 30 1.5 B6 loess-paleosol 30 1.5 A7 Q 3 loess 28 1.5 B7 loess-paleosol 28 1.5 A8 Q 3 loess 28 1.6 B8 loess-paleosol 28 1.6 The soil samples were placed into a homemade test device equipped with an electronic balance to monitor the amount of moisture lost in the sample and a high-definition digital camera to record the real-time process of cracks. The test device was then moved into an environment with a temperature of 20 ± 3°C and a relative humidity of 45%±3% for dehumidification treatment. The water loss of the soil samples during the test was recorded to monitor changes in water content, and the fracture development was documented with intercepted images. Adobe Photoshop software was used to preprocess the collected images, enhancing the clarity of fracture features for easier identification. To reduce the influence of edge shrinkage effects, the crack images were cropped by 5% in both width and length (final size: 54.6 cm × 36.1 cm). The crack Image Analysis System(CIAS), developed by Tang(20) et al., was used to analyze the crack images, obtaining key geometric parameters such as total crack length ( L ), average crack width ( D av ), and crack rate ( r ). After the fracture development stabilizes, the sample’s width is divided into 18 intervals along the Y direction, and the length is divided into 24 intervals along the X direction. Within each grid, the average water content of three soil samples is calculated for that position. This data is then used to create a water field distribution map. 3. Experimental Analysis 3.1 crack evolution Figure 1 and Fig. 2 illustrate the crack development process of Q 3 loess and loess-paleosol, using test groups A1 and B1 as examples. After 16 hours of dehumidification, the soil samples began to show obvious cracks. At this stage, the water content decreased rapidly, and the number of cracks increased continuously, but the increase in crack width was not significant. After 36 hours, the number of cracks increased slowly, the fracture skeleton was formed, and the cracks continued to widen. After 96 hours, the crack width developed very slowly. Although the cracks continued to widen, the crack shapes on the surface of the soil samples remained unchanged. At this point, it can be considered that the cracks have evolved into a complete development stage. Thus, the development of fractures can be divided into three stages: the initial development stage, the formation stage of the fracture skeleton, and the complete development stage. Comparing Fig. 1 and Fig. 2, it is evident that paleosol samples reached the stages of crack evolution earlier than Q 3 loess samples. The loess samples exhibited a stronger ability to generate secondary cracks and had a higher number of cracks. In contrast, the paleosol samples showed a weaker ability to generate secondary cracks, but the cracks were wider. 3.2 Moisture Distribution Post-Cracking After 108 hours of desiccation, grids were set for groups B2 and A2 ( w 0 = 30%, ρ d = 1.5g/cm -3 for paleosol and Q 3 loess, respectively) to measure water content. As shown in Fig. 3, group B2 (paleosol) averaged 12.78% moisture, with a range from 5.39–17.1%. Group A2 (loess) averaged 11.26%, ranging from 5.12–16.33%. Suction is a primary mechanical factor controlling crack formation (Tang 2008). The deformation characteristics of soil are closely related to changes in suction. The matric suction of paleosol and Q 3 loess increased as water content decreased. When cracks begin to develop, the water content at the crack initiation point decreases, causing suction to increase. This suction force drives soil moisture to migrate from the surrounding area to the crack point. The final water content distribution reflects the overall water migration process. Compared to Q 3 loess, paleosol samples have a lower crack density and higher clay content, which enhances their water retention capability. Although the water content at the main cracks of both soil samples is similar, the overall water content of the paleosol samples is higher. 3.3 Analysis of cracking difference between Q 3 loess and loess-paleosol Figure 4,5,6 illustrates the changes in crack rate, total crack length, and average crack width as water content decreases during the test. The results indicate that an increase in initial water content promotes higher crack rates, wider cracks, and longer total crack lengths. Conversely, an increase in dry density inhibits the increase in crack rate and total crack length but promotes wider cracks. Tables 3 and 4 show that initial water content has a greater influence than dry density. Q 3 loess and ancient soil exhibit similar overall trends in fracture development. Both types of soil crack at a certain water content, with the crack rate increasing as water content decreases, eventually stabilizing. However, ancient soil begins cracking at a higher water content and shows changes in crack rate at higher moisture levels. For instance, Q 3 loess cracks at a water content of 26%, with the crack rate curve flattening at 16%. This indicates that ancient soil has a greater overall shrinkage capacity, reflected in a higher crack rate. The higher clay content and stronger plasticity of ancient soil contribute to its greater shrinkage capacity compared to Q 3 loess. The increase in total fracture length is linked to the development of existing fractures and the formation of new ones. Unlike the crack rate versus water content curves, the total fracture length curve stabilizes at a higher water content. This is because the fracture framework is mostly developed at this stage, and fracture widening becomes the primary mode of shrinkage and deformation. Ancient soil specimens enter the widening stage at higher water content, while Q 3 loess specimens focus more on developing new cracks. The cracks in ancient soil are significantly wider than those in Q 3 loess. The deformation caused by water loss in paleosol primarily leads to the widening of existing cracks rather than creating new ones. The higher clay content in paleosol enhances their ability to shrink and deform with water loss, resulting in much wider cracks compared to Q 3 loess. There are significant differences in the cracking characteristics of Q 3 loess and paleosol under drought conditions. The water content of paleosol at the onset of cracking is higher, and the fracture rate is greater once cracking is complete. After water loss, Q 3 loess exhibits higher fracture density and quantity, but with relatively smaller crack widths. In contrast, paleosols have larger crack widths but lower crack density and quantity. This suggests that during water loss and shrinkage, paleosol primarily undergoes crack widening rather than the formation of new cracks. The larger crack width in paleosol is attributed to its higher clay content, which enhances its water loss shrinkage deformation capability. Table 3 Relationship between r f , L f , D av f , and initial water content r f /% w 0 /% r f max / r f min ρ d /g·cm -3 Types of loess r f max 5.55 30 1.32 1.5 Q 3 Loess r f min 4.20 26 If /cm L f max / L f min L f max 445.7 30 1.62 1.4 L f min 275.1 26 D av f /cm D av f max / D av f min D av f max 0.278 30 1.46 1.4 D av f min 0.190 26 r f /% r f max / r f min r f max 5.74 30 1.33 1.5 Loess paleo-soil r f min 4.31 26 If /cm L f max / L f min L f max 203.5 30 1.37 1.4 L f min 148.5 26 D av f /cm D av f max / D av f min D av f max 0.528 30 1.25 1.4 D av f min 0.422 26 Table 4 Relationship between r f , L , D av f , and dry density r f /% ρ d /g·cm -3 r f max / r f min w 0 /% Types of loess r f max 4.54 1.4 1.27 28 Q 3 Loess r f min 3.57 1.6 If /cm L f max / L f min L f max 445.7 1.4 1.27 30 L f min 350.9 1.6 D av f /cm D av f max / D av f min D av f max 0.355 1.6 1.28 30 D av f min 0.277 1.4 r f /% r f max / r f min r f max 5.16 1.4 1.17 28 Loess paleo-soil r f min 4.41 1.6 If /cm L f max / L f min L f max 203.5 1.4 1.37 30 L f min 148.5 1.6 D av f /cm D av f max / D av f min D av f max 0.584 1.6 1.11 30 D av f min 0.526 1.4 3) r f : Final crack rate 4) L f : Total final crack length 5) D av f : Average final crack width 4. Mechanism Analysis 4.1 Mechanical Mechanism of Fracture Differences Soil cracking is primarily controlled by the tensile strength and tensile force of the soil. The critical state of cracking can be described as $${\sigma _{\text{t}}}={T_{\text{S}}}$$ 1 Where ( σ t ) represents the tensile strength of the soil, and ( T S ) represents the tension caused by shrinkage deformation. There are significant differences in clay content between Q 3 loess and paleosol, leading to notable differences in soil strength and deformation ability. The existence of clay particles in soil can be categorized into two types, as shown in Fig. 4. The first type is a particle group composed solely of clay particles (Fig. 7(a)). In this mode, the clay particles are closely packed, resulting in a thin electric double layer on their surfaces(Lu 2014). This configuration leads to strong attraction and minimal repulsion between particles, thereby increasing the soil’s tensile strength. The second type involves clay particles connected to coarse particles to form a group (Fig. 7(b)). This mode creates a more compact connection between larger particles, further enhancing the soil’s tensile strength. From the above, it can be seen that the increase in tensile strength during a water loss is greater in loess paleosol compared to Q 3 loess, due to its higher clay content. The higher content of viscous particles in paleosol compared to Q 3 loess enhances its ability to deform through water loss and contraction. Viscous particles exhibit significant properties of water absorption and expansion(Gan 2018), as well as dehydration and contraction, leading to substantial volume changes in different states. During evaporation, the deformation of clay grains due to water loss causes the soil surface to contract and generate tension. These characteristics indicate that paleosol has a stronger deformation ability than Q 3 loess, resulting in greater surface tension during water loss. From the analysis, it is evident that paleosol has a higher clay content and a greater increase in tensile strength (T s) compared to Q 3 loess. To further understand the dominant factors in water loss and shrinkage cracking, the test data can be analyzed as follows: The water content at the onset of cracking for paleosol and Q 3 loess is 27% and 26%, respectively. The higher water content in paleosol indicates that the increase in clay particles leads to a greater increase in T s before and during the early stages of cracking. After crack development, the water content of paleosol and Q 3 loess samples is 17% and 16%, respectively. This suggests that Ts ceases to increase when the soil’s contraction and deformation stabilize. The higher tensile strength of paleosol compared to Q 3 loess allows it to reach a more stable state earlier. 4.2 Mechanism of Fracture Morphology Differences For a new crack created during evolution, the critical state of the crack tip in crack diffusion can be described as $$\left\{ \begin{gathered} K=\frac{{Y\sigma \sqrt {\pi a} }}{{1 - {\nu ^2}}} \hfill \\ K={K_{\text{c}}} \hfill \\ \end{gathered} \right.$$ 2 Where ( K c ) is the fracture toughness. The greater the fracture toughness, the less likely fracture diffusion will occur. According to the experimental study by Wang et al(2020)., there is a good linear fit between ( σ t ) and ( K c ), i.e., $${K_{\text{c}}}={b_{\text{t}}}{\sigma _{\text{t}}}$$ 3 Where ( b t ) is the fitting coefficient related to the sampling method. Combining this with the previous section, the tensile strength ( σ t ) of paleosol is larger than that of Q 3 loess. Therefore, the ( K c ) of loess should be larger than the ( K c ) of paleosol, indicating that the diffusion capacity of paleosol cracks is lower, and fewer secondary cracks are produced in general. The development and expansion of soil cracks are closely related to energy diffusion. The critical state of crack diffusion in paleosol can be used to calculate the critical energy release rate using the equation \(Gc=\frac{{dWs}}{{dA}}=2{\gamma _f}\) (4) where ( Gc ) denotes the fracture toughness of the soil, and ( Ws ) is the work required to produce a cracked surface, representing the fracture energy per unit area. According to Hallett's(2001) study on crack tip energy diffusion, soil samples with higher clay content have larger crack tip opening angles and greater energy driving crack diffusion compared to those with lower clay content. This suggests that paleosol has a weaker ability to generate new cracks and requires greater strain for crack diffusion compared to Q 3 loess. The behavior of a single crack can be described as the release of tensile stresses on a rigid substrate caused by the shrinkage of the paleosol. Essentially, there is a basal friction ( F ) that is equal to the tensile stress ( T ). Assume that T obeys Hooke's law, i.e. $$T=k\Delta x$$ 5 Where ( k ) is the modulus of elasticity and ( \(\Delta x\) ) is the deformation of the soil. As ( w ) decreases gradually with time ( t ), the relationship can be described using the elastic model equation proposed by Lecocq(2023): $$\frac{{D(w)}}{{{D_\infty }}}=(1 - {e^{ - (k/\alpha )[t({w_{{\text{cr}}}}) - t(w)]}})$$ 6 α is the friction coefficient, D ∞ is the final crack width, t ( w ) is the time needed to reach a certain water content, w cr is the critical water content when the crack development is completed, and the change of D (w) /D ∞ with w reflects the ability of crack widening of the soil body. Figure 8 shows the relationship curves between ( D (w)/ D ∞ ) and ( w ) for ancient soil and the Q 3 loess obtained from the test. Since the high water content stage primarily involves the development of the crack skeleton, changes in crack width are not significant. Therefore, the curve after ( w = 24% ) is selected. Figure 8 indicates that, at the same water content, the ( D (w)/ D ∞ ) of ancient soil is greater than that of Q3 loess. This means that during the crack widening process, under the same initial water content ( w 0 ) and dry density ( ρ d ), the final crack width of ancient soil is larger than that of Q 3 loess, and the water content is higher when crack development is completed. Compared to Q 3 loess, ancient soil has a higher proportion of small-sized particles and a smaller modulus of elasticity. During crack development, the crack width of ancient soil is larger than that of Q 3 loess at the same water content level. Mechanism analysis shows that the fracture widening capacity of Q 3 loess is greater than that of paleosol, which is consistent with the pattern observed in the test data. V. Conclusion Loess and paleosols undergo three stages of crack development after water loss: initiation, skeleton formation, and complete development. Compared to loess, paleosols initiate fractures earlier and have wider fractures, but fewer and less dense ones. After crack development is complete, moisture distribution shows that regions with higher water content have fewer cracks, while drier regions have more. Paleosols retain more water and exhibit higher cracking water content, whereas Q 3 loess has a higher density and number of cracks, but with smaller widths. Initial water content promotes the increase in fracture rate, total fracture length, and fracture width in both Q 3 loess and ancient soil samples. Dry density, on the other hand, inhibits fracture rate and total fracture length but promotes fracture width. The influence of initial water content is greater than that of dry density. Under the same initial water content and dry density conditions, Q 3 loess samples have a larger total crack length but smaller crack rate and width compared to ancient soil samples. Paleosol cracks earlier and reaches the complete development stage sooner. The drying and cracking of loess paleosols are primarily influenced by tension and soil tensile strength caused by soil deformation. Clay particles play a crucial role in increasing the soil's tensile strength and deformation capacity. Compared to Q 3 loesses, loess paleosols contain a higher content of clay particles. It is worth noting that tension and soil tensile strength play dominant roles in different phases of the cleavage evolution process. As a result, the cracking properties of loess paleosols and Q 3 loess exhibit significant differences. Additionally, an analysis based on fracture mechanics theory, the crack tip energy diffusion formula, and the soil cracking elasticity model indicate that loess paleosoil has a weaker ability to generate new cracks but superior deformation performance. These findings are consistent with the experimental results obtained. Declarations Author Contribution Y.X. wrote the main manuscript text. T.H.W. (Tie Hang Wang) and Z.K.Z. (Zai Kun Zhao) provided guidance on the experimental design and manuscript writing. All authors (Y.X., T.H.W., Z.K.Z.) reviewed the manuscript. References Wang Y, Li C H, Hu Y Z(2018) X-ray computed tomography (CT) observations of crack damage evolution in soil-rock mixture during uniaxial deformation, Arabian Journal of Geosciences 11: 1-13.https://doi.org/10.1007/s12517-018-3561-z Huang Z, Zhang H, Liu B, et al(2021) Using CT to test the damage characteristics of the internal structure of expansive soil induced by dry-wet cycles, AIP Advances 11(7)https://doi.org/10.1063/5.0057450 Sun X, Li X, Mao T, et al(2021) Fracture evolution analysis of soil-rock mixture in contrast with soil by CT scanning under uniaxial compressive conditions, Science China Technological Sciences 64(12): 2771-2780.https://doi.org/10.1007/s11431-020-1888-9 Zhao X, Li L, Yang B, et al(2022) Application of fractal to evaluate the drying shrinkage behavior of soil composites from recycled waste clay brick, Fractal, and Fractional 7(1): 25.https://doi.org/10.3390/fractalfract7010025 Fu X, Ding H, Sheng Q, et al(2022) Fractal Analysis of Particle Distribution and Scale Effect in a Soil–Rock Mixture, Fractal and Fractional 6(2): 120.https://doi.org/10.3390/fractalfract6020120 Tang, Y.; Yang, B.; Zhao, X.; Yang, C(2023) Structural and Fractal Analysis of Soil Cracks Due to the Roots of Setaria, Viridis. Fractal Fract. https://doi.org/10.3390/fractalfract7010019 Wu J, Yuan J, Ng C W W(2012) Theoretical and experimental study of the initial cracking mechanism of an expansive soil due to moisture-change, Journal of Central South University 19(5):1437-1446. https://doi.org/10.1007/s11771-012-1160-9 Menon S, Song X(2019) Coupled analysis of desiccation cracking in unsaturated soils through a non-local mathematical formulation, Geosciences 9(10): 428.https://doi.org/10.3390/geosciences9100428 Li G, Wang F, Ma W, et al(2018). Variations in strength and deformation of compacted loess exposed to wetting-drying and freeze-thaw cycles, Cold Regions Science and Technology 151:159-167.https://doi.org/10.1016/j.coldregions.2018.03.021 Zhou Z, Ma W, Zhang S, et al(2018) Effect of freeze-thaw cycles in mechanical behaviors of frozen loess, Cold Regions Science and Technology 146: 9-18.https://doi.org/10.1016/j.coldregions.2017.11.011 Feng L, Zhang M, Jin Z, et al(2021) The genesis, development, and evolution of original vertical joints in loess, Earth-Science Reviews 214: 103526.https://doi.org/10.1016/j.earscirev.2021.103526 Xu J, Hu K, Zhou L, et al(2023) Influence of wet-dry cycles on uniaxial compression behavior of fissured loess, Environmental Earth Sciences 82(1) : 5.https://doi.org/10.1007/s12665-022-10684-3 Tang D, Deng L, Fan W, et al(2024) Extension mechanism and failure mode investigation on a fissured loess slope induced by loading, Bulletin of Engineering Geology and the Environment 83(7): 294. https://doi.org/10.1007/s10064-024-03787-7 Abbaszadeh M M, Houston S L, Zapata C E(2015) Influence of soil cracking on the soil-water characteristic curve of clay soil, Soils, and Rocks 38(1): 49-58.https://doi.org/10.28927/SR.381049 Li Z, Wang S, Jin L(2019) Experimental Study on the Effects of Coarse Particles on Cracking Behavior of Clay, Journal of Yangtze River Scientific Research Institute 36(6):99-105.https://doi.org/10.11988/ckyyb.20171218 Zhong Y, Cai G, Zeng G(2022) The effect of initial water content and density on the swelling-shrinkage and cracking characteristics of compacted clay, Separations 9(12): 424.https://doi.org/10.3390/separations9120424 Schmidinger J, Schröter I, Bönecke E, et al(2024) Effect of training sample size, sampling design and prediction model on soil mapping with proximal sensing data for precision liming, Precision Agriculture 25(3): 1529-1555. https://doi.org/10.1007/s11119-024-10122-3 Luo Z, Wang S, Zhang J, Yang Z ,et al(2020) Thickness effect on crack evolution of expansive soil, Chinese Journal of Geotechnical Engineering 42(10): 1922-1930.https://doi.org/10.11779/CJGE202010018 Liu J, Tang C, Zeng H, et al(2021) Evolution of desiccation cracking behavior of clays under drying-wetting cycles, Rock and Soil Mechanics 42(10): 2763-2772.https://doi.org/10.16285/j.rsm.2021.5459 Tang C, Shi B, Liu C, et al(2008) Influencing factors of geometrical structure of surface shrinkage cracks in clayey soils, Engineering Geology, 101(3-4):204-217.https://doi.org/10.1016/j.enggeo.2008.05.005 Tang C, Shi B, Cui Y(2018) Behaviors and mechanisms of desiccation cracking of soils, Chinese Journal of Geotechnical Engineering, 40(8):1415-1423.https://doi.org/10.11779/CJGE201808006 Lu L, Fan H, Chen H, et al(2014) Influencing factors for uniaxial tensile strength of dispersive soils, Chinese Journal of Geotechnical Engineering 36(6):1160-1166.https://doi.org/10.11779/CJGE201406023 Gan F, Hang X, Liu Y, Ma Y(2018) Physicochemical and Mineralogical Properties of Bentonites in South Jiangsu, China, Acta Pedologica Sinica 55(4):945-954.https://doi.org/10.11766/trxb201711240517 Wang J, Huang S, Guo W,et al(2020) Experimental study on fracture toughness of a compacted clay using semi-circular bend specimen, Engineering Fracture Mechanics 224:106814.https://doi.org/10.1016/j.engfracmech.2019.106814 Hallett P D, Newson T A(2001) A simple fracture mechanics approach for assessing ductile crack growth in soil, Soil Science Society of America Journal, 65(4):1083-1088.https://doi.org/10.2136/sssaj2001.6541083x Lecocq N, Vandewalle N(2023) Dynamics of crack opening in a one-dimensional desiccation experiment, Physica A: Statistical Mechanics and its Applications, 321(3): 431-441.https://doi.org/10.1016/S0378-4371(02)01538-8 Additional Declarations No competing interests reported. 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Xing","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2ElEQVRIiWNgGAWjYDACZjBpg8olRksaiGBsIE4LBBwmQYvBcd7Dr3nbzif2z0h+/oChwjqxgf3sAbxaJJv50qx5224bS9xIM2xgOJOe2MCTl4BXCz8zj5kxUIscw40EwwbGtsOJDRI8Bni1sEG0nOORv5H+sYHxHxFagLYYP+ZtOyBncCMHaEsDEVokm3nMGOecSzY2PPOmcEbCsXTjNp4c/FoMzp8x/vCmzC5x3vH0DR8+1FjL9rOfwa8F5B0pHhgzAcQlpB4ImD/+IELVKBgFo2AUjGAAACejQaOULthiAAAAAElFTkSuQmCC","orcid":"","institution":"Xi'an University of Architecture and Technology","correspondingAuthor":true,"prefix":"","firstName":"Yu","middleName":"","lastName":"Xing","suffix":""},{"id":368291093,"identity":"7d760048-222b-4ef4-8091-0f86b7a84a07","order_by":1,"name":"Tie Hang Wang","email":"","orcid":"","institution":"Xi'an University of Architecture and Technology","correspondingAuthor":false,"prefix":"","firstName":"Tie","middleName":"Hang","lastName":"Wang","suffix":""},{"id":368291094,"identity":"8aadc699-53c6-4782-911f-50e83cfe3bea","order_by":2,"name":"Zai Kun Zhao","email":"","orcid":"","institution":"Guangxi University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Zai","middleName":"Kun","lastName":"Zhao","suffix":""}],"badges":[],"createdAt":"2024-10-19 13:23:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5294720/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5294720/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":67922634,"identity":"8eb1448a-8594-4c36-ad07-e4abf693a8e8","added_by":"auto","created_at":"2024-10-31 08:20:04","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":241816,"visible":true,"origin":"","legend":"\u003cp\u003eCracking process of the paleosoil specimens\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5294720/v1/b65eb496385386ede6cd109f.png"},{"id":67922635,"identity":"1e6a9ca4-fa19-443b-bd14-e9dbf1c27dbe","added_by":"auto","created_at":"2024-10-31 08:20:04","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":254735,"visible":true,"origin":"","legend":"\u003cp\u003eCracking process of the Q\u003csub\u003e3\u003c/sub\u003e loess specimen\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5294720/v1/ab65ba747b90b64bdbdceaef.png"},{"id":67922640,"identity":"61edd431-dafa-427c-bbf8-db349a50c7b9","added_by":"auto","created_at":"2024-10-31 08:20:05","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":148471,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of moisture fields in loess and paleosoil samples after completion of crack development\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5294720/v1/913de16003ef20f06f163a40.png"},{"id":67922639,"identity":"5457452e-4f3f-44c3-b9ac-1768ed2ff60d","added_by":"auto","created_at":"2024-10-31 08:20:05","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":61595,"visible":true,"origin":"","legend":"\u003cp\u003eCrack rate changes during fissure evolution\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5294720/v1/374fc9a5f46ba305207f6ff8.png"},{"id":67923667,"identity":"aa7ef00e-ccff-4265-9997-a405deb3b1b6","added_by":"auto","created_at":"2024-10-31 08:28:05","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":67157,"visible":true,"origin":"","legend":"\u003cp\u003eTotal crack length changes during fissure evolution\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5294720/v1/276f81768e8cd72d1e5e0d4f.png"},{"id":67923665,"identity":"42706344-ee2b-45c7-8753-70687bb141f0","added_by":"auto","created_at":"2024-10-31 08:28:04","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":71126,"visible":true,"origin":"","legend":"\u003cp\u003eAverage crack width changes during fissure evolution\u003c/p\u003e\n\u003cp\u003e1）\u003cem\u003e\u003cstrong\u003ew\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cstrong\u003e0\u003c/strong\u003e\u003c/sub\u003e: Initial water content\u003c/p\u003e\n\u003cp\u003e2）\u003cem\u003e\u003cstrong\u003eρ\u003c/strong\u003e\u003c/em\u003e\u003csub\u003e\u003cstrong\u003ed\u003c/strong\u003e\u003c/sub\u003e: Dry density\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5294720/v1/a7125459bce60759b7681680.png"},{"id":67922637,"identity":"0178c609-d62b-43db-a20c-6d3960c6299f","added_by":"auto","created_at":"2024-10-31 08:20:04","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":42247,"visible":true,"origin":"","legend":"\u003cp\u003eMode of the existence of viscous particles\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5294720/v1/f445a5a1f9e88af1535bfd27.png"},{"id":67923666,"identity":"748486f8-f473-440d-8318-ae3a98ac0e48","added_by":"auto","created_at":"2024-10-31 08:28:04","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":23624,"visible":true,"origin":"","legend":"\u003cp\u003eCurve of \u003cem\u003eD\u003c/em\u003e(w)/\u003cem\u003eD\u003c/em\u003e\u003csub\u003e∞\u003c/sub\u003e vs. w for crack widening stage\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5294720/v1/4b47ba05356233442304d0c1.png"},{"id":69753725,"identity":"e6b7d3f4-1a28-4efc-878f-f6fc3ff5b5ba","added_by":"auto","created_at":"2024-11-25 02:47:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1517550,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5294720/v1/ecc8555a-0df8-403e-aad2-492ee49abd85.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Crack Evolution and its Quantitative Analysis on Unsaturated Loess and Paleosoil","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003ePaleosols in loess regions are soil layers formed during periods of aeolian accumulation under alternating dry and wet climatic conditions. Biological growth during these periods significantly influenced soil formation, resulting in a high content of cohesive particles. These paleosols are notably prone to cracking. When exposed, they become more unstable after dehydration cracking compared to typical loess. This instability can lead to severe environmental disasters, such as weathering grooves on loess slopes and instability around tunnel entrances.\u003c/p\u003e \u003cp\u003eExpansive soils are known for their distinct desiccation shrinkage and cracking characteristics. Most studies on desiccation cracking focus on expansive soils, using methods like CT scanning to observe internal soil fracture(Wang 2018; Huang 2021), graphic analysis software for fracture data processing(Sun 2021), fractal theory for evaluating cracking(Zhao 2022; Fu 2022; Tang 2023), and elastic mechanics theory-based models for cracking(Wu 2012; Menon \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn contrast, existing loess research predominantly investigates native cracks and changes in engineering properties resulting from factors like loading, freeze-thaw cycles, and wet-dry cycles. For instance, Li(2018) examined fracture evolution in loess under freeze-thaw and wet-dry conditions. Zhou(2018) investigated these properties in loess samples exposed to freeze-thaw cycles. Feng(2021) developed a 3D creep constitutive model for native loess within crack zones. Similarly, Xu(2023) studied engineering properties such as volume, void ratio, and collapsible settlement of loess samples subjected to freeze-thaw cycles. Additionally, Tang(2024) explored deformation characteristics, stress variations, and failure modes in loess slopes induced by loading.\u003c/p\u003e \u003cp\u003eSignificant differences in particle size distribution exist between Q\u003csub\u003e3\u003c/sub\u003e loess and remolded paleosol soils. Studies on the impact of clay content on soil cracking often consider factors like soil water content and dry density. For instance, Abbaszadeh(2015) investigates how different clay contents and water contents affect the development of cracks and the hydraulic properties of the soil. Li(2019) examined the influence of coarse particles on the cracking of cohesive soils. Zhong(2022) focuses on the effects of initial water content and dry density on the shrinkage and cracking behavior of compacted clay. These studies highlight the critical impact of particle size distribution on soil cracking. However, the distinctive soil composition and deformation characteristics of loess paleosols compared to other soils make it challenging to evaluate their fracture evolution characteristics.\u003c/p\u003e \u003cp\u003eThe study of fracture evolution characteristics of loess paleosols under dehydration shrinkage conditions, and their differences from Q\u003csub\u003e3\u003c/sub\u003e loess, is of significant importance. The authors prepared large-sized compacted samples of Q\u003csub\u003e3\u003c/sub\u003e loess and paleosols and conducted comparative experiments on fracture evolution under ambient drying conditions. Fracture development was recorded in real-time, and a moisture field model was established by dividing the area into grids. High-definition cameras were used to compare the fracture evolution patterns of loess and paleosols under dry conditions in detail, further exploring the underlying mechanisms.\u003c/p\u003e"},{"header":"2 Samples and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Sample Preparation\u003c/h2\u003e \u003cp\u003eThe Q\u003csub\u003e3\u003c/sub\u003e loess used in the test was sourced from a construction site in Xianyang, China, while the loess-paleosol was taken from a highway construction section in Weinan, China. Both types of test soils are widely distributed in the loess area. The physical indexes of the soils obtained from the geotechnical tests are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e:\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\u003ePhysical properties of Q3 loess and paleosol\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=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTypes of loess\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eliquid limit, w\u003csub\u003eL\u003c/sub\u003e/%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eplastic limit, w\u003csub\u003eP\u003c/sub\u003e/%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eplasticity index, I\u003csub\u003eP\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e loess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e29.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e11.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLoess paleosol\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e32.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e18.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e13.8\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\u003eDuring dehumidification, the overall shrinkage of small-sized models significantly affects size changes(2024). This shrinkage constrains the formation of surface cracks and impacts test results. The thickness of the soil layer also influences quantitative parameters such as the number of nodes and cracks in the fracture network(2020). Samples with greater thickness exhibit single, wide fractures with a pronounced boundary effect. To minimize these influences on result statistics, the test refers to the model design of Liu(2021) and uses a large-sized model with dimensions of 575mm \u0026times; 380mm \u0026times; 20mm, resulting in a width-thickness ratio of only 0.053.\u003c/p\u003e \u003cp\u003eBy geotechnical testing standards, soil samples were air-dried, crushed, and sieved. The required amount was weighed and mixed with deionized water to achieve a specific water content. The mixture was left to stand for 24 hours to ensure uniform moisture distribution. The soil was then placed in a mold and compacted to a thickness of 20mm. The open side was covered with cling film, which was removed after 24 hours to prepare for testing.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Experimental Scheme\u003c/h2\u003e \u003cp\u003eThe experiment considers the impact of initial water content and dry density on soil cracking. The parameters are set as shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e:\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 group parameter setting\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=\"left\" 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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumber\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTypes of loess\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eInitial water content,\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({w_0}\\)\u003c/span\u003e\u003c/span\u003e/%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSoil dry density,\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\rho _{\\text{d}}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003cp\u003e/g\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e loess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eloess-paleosol\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e loess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eloess-paleosol\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e loess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eloess-paleosol\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e loess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eloess-paleosol\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e loess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eloess-paleosol\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e loess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eloess-paleosol\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e loess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eloess-paleosol\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e loess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eloess-paleosol\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.6\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\u003eThe soil samples were placed into a homemade test device equipped with an electronic balance to monitor the amount of moisture lost in the sample and a high-definition digital camera to record the real-time process of cracks. The test device was then moved into an environment with a temperature of 20\u0026thinsp;\u0026plusmn;\u0026thinsp;3\u0026deg;C and a relative humidity of 45%\u0026plusmn;3% for dehumidification treatment.\u003c/p\u003e \u003cp\u003eThe water loss of the soil samples during the test was recorded to monitor changes in water content, and the fracture development was documented with intercepted images. Adobe Photoshop software was used to preprocess the collected images, enhancing the clarity of fracture features for easier identification. To reduce the influence of edge shrinkage effects, the crack images were cropped by 5% in both width and length (final size: 54.6 cm \u0026times; 36.1 cm). The crack Image Analysis System(CIAS), developed by Tang(20) et al., was used to analyze the crack images, obtaining key geometric parameters such as total crack length (\u003cem\u003eL\u003c/em\u003e), average crack width (\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e), and crack rate (\u003cem\u003er\u003c/em\u003e).\u003c/p\u003e \u003cp\u003eAfter the fracture development stabilizes, the sample\u0026rsquo;s width is divided into 18 intervals along the Y direction, and the length is divided into 24 intervals along the X direction. Within each grid, the average water content of three soil samples is calculated for that position. This data is then used to create a water field distribution map.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Experimental Analysis","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003e3.1 crack evolution\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eFigure 1 and Fig.\u0026nbsp;2 illustrate the crack development process of Q\u003csub\u003e3\u003c/sub\u003e loess and loess-paleosol, using test groups A1 and B1 as examples. After 16 hours of dehumidification, the soil samples began to show obvious cracks. At this stage, the water content decreased rapidly, and the number of cracks increased continuously, but the increase in crack width was not significant. After 36 hours, the number of cracks increased slowly, the fracture skeleton was formed, and the cracks continued to widen. After 96 hours, the crack width developed very slowly. Although the cracks continued to widen, the crack shapes on the surface of the soil samples remained unchanged. At this point, it can be considered that the cracks have evolved into a complete development stage. Thus, the development of fractures can be divided into three stages: the initial development stage, the formation stage of the fracture skeleton, and the complete development stage.\u003c/p\u003e \u003cp\u003eComparing Fig.\u0026nbsp;1 and Fig.\u0026nbsp;2, it is evident that paleosol samples reached the stages of crack evolution earlier than Q\u003csub\u003e3\u003c/sub\u003e loess samples. The loess samples exhibited a stronger ability to generate secondary cracks and had a higher number of cracks. In contrast, the paleosol samples showed a weaker ability to generate secondary cracks, but the cracks were wider.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Moisture Distribution Post-Cracking\u003c/h2\u003e \u003cp\u003eAfter 108 hours of desiccation, grids were set for groups B2 and A2 (\u003cem\u003ew\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;30%, \u003cem\u003eρ\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;1.5g/cm\u003csup\u003e-3\u003c/sup\u003e for paleosol and Q\u003csub\u003e3\u003c/sub\u003e loess, respectively) to measure water content. As shown in Fig.\u0026nbsp;3, group B2 (paleosol) averaged 12.78% moisture, with a range from 5.39\u0026ndash;17.1%. Group A2 (loess) averaged 11.26%, ranging from 5.12\u0026ndash;16.33%.\u003c/p\u003e \u003cp\u003eSuction is a primary mechanical factor controlling crack formation (Tang 2008). The deformation characteristics of soil are closely related to changes in suction. The matric suction of paleosol and Q\u003csub\u003e3\u003c/sub\u003e loess increased as water content decreased. When cracks begin to develop, the water content at the crack initiation point decreases, causing suction to increase. This suction force drives soil moisture to migrate from the surrounding area to the crack point. The final water content distribution reflects the overall water migration process.\u003c/p\u003e \u003cp\u003eCompared to Q\u003csub\u003e3\u003c/sub\u003e loess, paleosol samples have a lower crack density and higher clay content, which enhances their water retention capability. Although the water content at the main cracks of both soil samples is similar, the overall water content of the paleosol samples is higher.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Analysis of cracking difference between Q\u003csub\u003e3\u003c/sub\u003e loess and loess-paleosol\u003c/h2\u003e \u003cp\u003eFigure 4,5,6 illustrates the changes in crack rate, total crack length, and average crack width as water content decreases during the test. The results indicate that an increase in initial water content promotes higher crack rates, wider cracks, and longer total crack lengths. Conversely, an increase in dry density inhibits the increase in crack rate and total crack length but promotes wider cracks. Tables\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and \u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e show that initial water content has a greater influence than dry density.\u003c/p\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e loess and ancient soil exhibit similar overall trends in fracture development. Both types of soil crack at a certain water content, with the crack rate increasing as water content decreases, eventually stabilizing. However, ancient soil begins cracking at a higher water content and shows changes in crack rate at higher moisture levels. For instance, Q\u003csub\u003e3\u003c/sub\u003e loess cracks at a water content of 26%, with the crack rate curve flattening at 16%. This indicates that ancient soil has a greater overall shrinkage capacity, reflected in a higher crack rate. The higher clay content and stronger plasticity of ancient soil contribute to its greater shrinkage capacity compared to Q\u003csub\u003e3\u003c/sub\u003e loess.\u003c/p\u003e \u003cp\u003eThe increase in total fracture length is linked to the development of existing fractures and the formation of new ones. Unlike the crack rate versus water content curves, the total fracture length curve stabilizes at a higher water content. This is because the fracture framework is mostly developed at this stage, and fracture widening becomes the primary mode of shrinkage and deformation. Ancient soil specimens enter the widening stage at higher water content, while Q\u003csub\u003e3\u003c/sub\u003e loess specimens focus more on developing new cracks.\u003c/p\u003e \u003cp\u003eThe cracks in ancient soil are significantly wider than those in Q\u003csub\u003e3\u003c/sub\u003e loess. The deformation caused by water loss in paleosol primarily leads to the widening of existing cracks rather than creating new ones. The higher clay content in paleosol enhances their ability to shrink and deform with water loss, resulting in much wider cracks compared to Q\u003csub\u003e3\u003c/sub\u003e loess.\u003c/p\u003e \u003cp\u003eThere are significant differences in the cracking characteristics of Q\u003csub\u003e3\u003c/sub\u003e loess and paleosol under drought conditions. The water content of paleosol at the onset of cracking is higher, and the fracture rate is greater once cracking is complete. After water loss, Q\u003csub\u003e3\u003c/sub\u003e loess exhibits higher fracture density and quantity, but with relatively smaller crack widths. In contrast, paleosols have larger crack widths but lower crack density and quantity. This suggests that during water loss and shrinkage, paleosol primarily undergoes crack widening rather than the formation of new cracks. The larger crack width in paleosol is attributed to its higher clay content, which enhances its water loss shrinkage deformation capability.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRelationship between \u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e,\u003c/sup\u003e and initial water content\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=\"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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e /%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003ew\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e/%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e/\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eρ\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e/g\u0026middot;cm\u003csup\u003e-3\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eTypes of loess\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"7\" rowspan=\"8\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e Loess\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eIf\u003c/em\u003e /cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e/\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e445.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e275.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e /cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emax\u003c/sub\u003e/ \u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emin\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emax\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.278\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emin\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.190\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e /%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e/\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"7\" rowspan=\"8\"\u003e \u003cp\u003eLoess paleo-soil\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eIf\u003c/em\u003e /cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e/\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e203.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e148.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e \u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e/cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emax\u003c/sub\u003e/ \u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emin\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emax\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.528\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emin\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.422\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26\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=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRelationship between \u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eL\u003c/em\u003e, \u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e,\u003c/sup\u003e and dry density\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=\"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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e /%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eρ\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e/g\u0026middot;cm\u003csup\u003e-3\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e/\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003ew\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e/%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eTypes of loess\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"7\" rowspan=\"8\"\u003e \u003cp\u003eQ\u003csub\u003e3\u003c/sub\u003e Loess\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eIf\u003c/em\u003e /cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e/\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e445.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e350.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e /cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emax\u003c/sub\u003e/ \u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emin\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emax\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.355\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emin\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.277\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e /%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e/\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"7\" rowspan=\"8\"\u003e \u003cp\u003eLoess paleo-soil\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eIf\u003c/em\u003e /cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e/\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e max\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e203.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e min\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e148.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e /cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emax\u003c/sub\u003e/ \u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emin\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emax\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.584\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e\u003csup\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sup\u003e\u003csub\u003emin\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.526\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003cdiv class=\"Heading\"\u003e3)\u003cb\u003er\u003c/b\u003e\u003csub\u003e\u003cb\u003ef\u003c/b\u003e\u003c/sub\u003e: Final crack rate\u003c/div\u003e\n\u003cdiv class=\"Heading\"\u003e4)\u003cb\u003eL\u003c/b\u003e\u003csub\u003e\u003cb\u003ef\u003c/b\u003e\u003c/sub\u003e: Total final crack length\u003c/div\u003e\n\u003cdiv class=\"Heading\"\u003e5)\u003cb\u003eD\u003c/b\u003e\u003csub\u003e\u003cb\u003eav\u003c/b\u003e\u003c/sub\u003e\u003csup\u003e\u003cb\u003ef\u003c/b\u003e\u003c/sup\u003e: Average final crack width\u003c/div\u003e"},{"header":"4. Mechanism Analysis","content":"\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Mechanical Mechanism of Fracture Differences\u003c/h2\u003e \u003cp\u003eSoil cracking is primarily controlled by the tensile strength and tensile force of the soil. The critical state of cracking can be described as\u003c/p\u003e\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$${\\sigma _{\\text{t}}}={T_{\\text{S}}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e \u003cp\u003eWhere ( \u003cem\u003eσ\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e ) represents the tensile strength of the soil, and (\u003cem\u003eT\u003c/em\u003e\u003csub\u003eS\u003c/sub\u003e) represents the tension caused by shrinkage deformation. There are significant differences in clay content between Q\u003csub\u003e3\u003c/sub\u003e loess and paleosol, leading to notable differences in soil strength and deformation ability.\u003c/p\u003e \u003cp\u003eThe existence of clay particles in soil can be categorized into two types, as shown in Fig.\u0026nbsp;4. The first type is a particle group composed solely of clay particles (Fig.\u0026nbsp;7(a)). In this mode, the clay particles are closely packed, resulting in a thin electric double layer on their surfaces(Lu 2014). This configuration leads to strong attraction and minimal repulsion between particles, thereby increasing the soil’s tensile strength.\u003c/p\u003e \u003cp\u003eThe second type involves clay particles connected to coarse particles to form a group (Fig.\u0026nbsp;7(b)). This mode creates a more compact connection between larger particles, further enhancing the soil’s tensile strength.\u003c/p\u003e \u003cp\u003eFrom the above, it can be seen that the increase in tensile strength during a water loss is greater in loess paleosol compared to Q\u003csub\u003e3\u003c/sub\u003e loess, due to its higher clay content.\u003c/p\u003e \u003cp\u003eThe higher content of viscous particles in paleosol compared to Q\u003csub\u003e3\u003c/sub\u003e loess enhances its ability to deform through water loss and contraction. Viscous particles exhibit significant properties of water absorption and expansion(Gan 2018), as well as dehydration and contraction, leading to substantial volume changes in different states. During evaporation, the deformation of clay grains due to water loss causes the soil surface to contract and generate tension. These characteristics indicate that paleosol has a stronger deformation ability than Q\u003csub\u003e3\u003c/sub\u003e loess, resulting in greater surface tension during water loss.\u003c/p\u003e \u003cp\u003eFrom the analysis, it is evident that paleosol has a higher clay content and a greater increase in tensile strength \u003cem\u003e(T\u003c/em\u003es) compared to Q\u003csub\u003e3\u003c/sub\u003e loess. To further understand the dominant factors in water loss and shrinkage cracking, the test data can be analyzed as follows:\u003c/p\u003e \u003cp\u003eThe water content at the onset of cracking for paleosol and Q\u003csub\u003e3\u003c/sub\u003e loess is 27% and 26%, respectively. The higher water content in paleosol indicates that the increase in clay particles leads to a greater increase in \u003cem\u003eT\u003c/em\u003es before and during the early stages of cracking.\u003c/p\u003e \u003cp\u003eAfter crack development, the water content of paleosol and Q\u003csub\u003e3\u003c/sub\u003e loess samples is 17% and 16%, respectively. This suggests that Ts ceases to increase when the soil’s contraction and deformation stabilize. The higher tensile strength of paleosol compared to Q\u003csub\u003e3\u003c/sub\u003e loess allows it to reach a more stable state earlier.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Mechanism of Fracture Morphology Differences\u003c/h2\u003e \u003cp\u003eFor a new crack created during evolution, the critical state of the crack tip in crack diffusion can be described as\u003c/p\u003e\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\left\\{ \\begin{gathered} K=\\frac{{Y\\sigma \\sqrt {\\pi a} }}{{1 - {\\nu ^2}}} \\hfill \\\\ K={K_{\\text{c}}} \\hfill \\\\ \\end{gathered} \\right.$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e \u003cp\u003eWhere ( \u003cem\u003eK\u003c/em\u003e\u003csub\u003ec\u003c/sub\u003e ) is the fracture toughness. The greater the fracture toughness, the less likely fracture diffusion will occur. According to the experimental study by Wang et al(2020)., there is a good linear fit between ( \u003cem\u003eσ\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e ) and ( \u003cem\u003eK\u003c/em\u003e\u003csub\u003ec\u003c/sub\u003e ), i.e.,\u003c/p\u003e\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$${K_{\\text{c}}}={b_{\\text{t}}}{\\sigma _{\\text{t}}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e \u003cp\u003eWhere ( \u003cem\u003eb\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e ) is the fitting coefficient related to the sampling method.\u003c/p\u003e \u003cp\u003eCombining this with the previous section, the tensile strength ( \u003cem\u003eσ\u003c/em\u003e\u003csub\u003et\u003c/sub\u003e ) of paleosol is larger than that of Q\u003csub\u003e3\u003c/sub\u003e loess. Therefore, the ( \u003cem\u003eK\u003c/em\u003e\u003csub\u003ec\u003c/sub\u003e ) of loess should be larger than the ( \u003cem\u003eK\u003c/em\u003e\u003csub\u003ec\u003c/sub\u003e ) of paleosol, indicating that the diffusion capacity of paleosol cracks is lower, and fewer secondary cracks are produced in general.\u003c/p\u003e \u003cp\u003eThe development and expansion of soil cracks are closely related to energy diffusion. The critical state of crack diffusion in paleosol can be used to calculate the critical energy release rate using the equation\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(Gc=\\frac{{dWs}}{{dA}}=2{\\gamma _f}\\)\u003c/span\u003e\u003c/span\u003e (4)\u003c/p\u003e \u003cp\u003ewhere ( \u003cem\u003eGc\u003c/em\u003e ) denotes the fracture toughness of the soil, and ( \u003cem\u003eWs\u003c/em\u003e ) is the work required to produce a cracked surface, representing the fracture energy per unit area. According to Hallett's(2001) study on crack tip energy diffusion, soil samples with higher clay content have larger crack tip opening angles and greater energy driving crack diffusion compared to those with lower clay content. This suggests that paleosol has a weaker ability to generate new cracks and requires greater strain for crack diffusion compared to Q\u003csub\u003e3\u003c/sub\u003e loess.\u003c/p\u003e \u003cp\u003eThe behavior of a single crack can be described as the release of tensile stresses on a rigid substrate caused by the shrinkage of the paleosol. Essentially, there is a basal friction ( \u003cem\u003eF\u003c/em\u003e ) that is equal to the tensile stress ( \u003cem\u003eT\u003c/em\u003e ).\u003c/p\u003e \u003cp\u003eAssume that \u003cem\u003eT\u003c/em\u003e obeys Hooke's law, i.e.\u003c/p\u003e\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$T=k\\Delta x$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e5\u003c/div\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e \u003cp\u003eWhere ( \u003cem\u003ek\u003c/em\u003e ) is the modulus of elasticity and ( \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\Delta x\\)\u003c/span\u003e\u003c/span\u003e ) is the deformation of the soil. As ( \u003cem\u003ew\u003c/em\u003e ) decreases gradually with time ( \u003cem\u003et\u003c/em\u003e ), the relationship can be described using the elastic model equation proposed by Lecocq(2023):\u003c/p\u003e\u003cdiv id=\"Equ5\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ5\" name=\"EquationSource\"\u003e\n$$\\frac{{D(w)}}{{{D_\\infty }}}=(1 - {e^{ - (k/\\alpha )[t({w_{{\\text{cr}}}}) - t(w)]}})$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e6\u003c/div\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e \u003cp\u003e \u003cem\u003eα\u003c/em\u003e is the friction coefficient, \u003cem\u003eD\u003c/em\u003e\u003csub\u003e∞\u003c/sub\u003e is the final crack width, \u003cem\u003et\u003c/em\u003e(\u003cem\u003ew\u003c/em\u003e) is the time needed to reach a certain water content, \u003cem\u003ew\u003c/em\u003e\u003csub\u003ecr\u003c/sub\u003e is the critical water content when the crack development is completed, and the change of \u003cem\u003eD\u003c/em\u003e(w)\u003cem\u003e/D\u003c/em\u003e\u003csub\u003e\u003cem\u003e∞\u003c/em\u003e\u003c/sub\u003e with w reflects the ability of crack widening of the soil body.\u003c/p\u003e \u003cp\u003eFigure 8 shows the relationship curves between ( \u003cem\u003eD\u003c/em\u003e(w)/\u003cem\u003eD\u003c/em\u003e\u003csub\u003e∞\u003c/sub\u003e ) and ( \u003cem\u003ew\u003c/em\u003e ) for ancient soil and the Q\u003csub\u003e3\u003c/sub\u003e loess obtained from the test. Since the high water content stage primarily involves the development of the crack skeleton, changes in crack width are not significant. Therefore, the curve after ( \u003cem\u003ew\u003c/em\u003e = 24% ) is selected.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;8 indicates that, at the same water content, the ( \u003cem\u003eD\u003c/em\u003e(w)/\u003cem\u003eD\u003c/em\u003e\u003csub\u003e∞\u003c/sub\u003e ) of ancient soil is greater than that of Q3 loess. This means that during the crack widening process, under the same initial water content ( \u003cem\u003ew\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e ) and dry density ( \u003cem\u003eρ\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e ), the final crack width of ancient soil is larger than that of Q\u003csub\u003e3\u003c/sub\u003e loess, and the water content is higher when crack development is completed.\u003c/p\u003e \u003cp\u003eCompared to Q\u003csub\u003e3\u003c/sub\u003e loess, ancient soil has a higher proportion of small-sized particles and a smaller modulus of elasticity. During crack development, the crack width of ancient soil is larger than that of Q\u003csub\u003e3\u003c/sub\u003e loess at the same water content level. Mechanism analysis shows that the fracture widening capacity of Q\u003csub\u003e3\u003c/sub\u003e loess is greater than that of paleosol, which is consistent with the pattern observed in the test data.\u003c/p\u003e \u003c/div\u003e"},{"header":"V. Conclusion","content":"\u003cp\u003eLoess and paleosols undergo three stages of crack development after water loss: initiation, skeleton formation, and complete development. Compared to loess, paleosols initiate fractures earlier and have wider fractures, but fewer and less dense ones.\u003c/p\u003e\u003cp\u003eAfter crack development is complete, moisture distribution shows that regions with higher water content have fewer cracks, while drier regions have more. Paleosols retain more water and exhibit higher cracking water content, whereas Q\u003csub\u003e3\u003c/sub\u003e loess has a higher density and number of cracks, but with smaller widths.\u003c/p\u003e\u003cp\u003eInitial water content promotes the increase in fracture rate, total fracture length, and fracture width in both Q\u003csub\u003e3\u003c/sub\u003e loess and ancient soil samples. Dry density, on the other hand, inhibits fracture rate and total fracture length but promotes fracture width. The influence of initial water content is greater than that of dry density. Under the same initial water content and dry density conditions, Q\u003csub\u003e3\u003c/sub\u003e loess samples have a larger total crack length but smaller crack rate and width compared to ancient soil samples. Paleosol cracks earlier and reaches the complete development stage sooner.\u003c/p\u003e\u003cp\u003eThe drying and cracking of loess paleosols are primarily influenced by tension and soil tensile strength caused by soil deformation. Clay particles play a crucial role in increasing the soil's tensile strength and deformation capacity. Compared to Q\u003csub\u003e3\u003c/sub\u003e loesses, loess paleosols contain a higher content of clay particles. It is worth noting that tension and soil tensile strength play dominant roles in different phases of the cleavage evolution process. As a result, the cracking properties of loess paleosols and Q\u003csub\u003e3\u003c/sub\u003e loess exhibit significant differences. Additionally, an analysis based on fracture mechanics theory, the crack tip energy diffusion formula, and the soil cracking elasticity model indicate that loess paleosoil has a weaker ability to generate new cracks but superior deformation performance. These findings are consistent with the experimental results obtained.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eY.X. wrote the main manuscript text. T.H.W. (Tie Hang Wang) and Z.K.Z. (Zai Kun Zhao) provided guidance on the experimental design and manuscript writing. All authors (Y.X., T.H.W., Z.K.Z.) reviewed the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eWang Y, Li C H, Hu Y Z(2018) X-ray computed tomography (CT) observations of crack damage evolution in soil-rock mixture during uniaxial deformation, Arabian Journal of Geosciences 11: 1-13.https://doi.org/10.1007/s12517-018-3561-z\u003c/li\u003e\n\u003cli\u003eHuang Z, Zhang H, Liu B, et al(2021) Using CT to test the damage characteristics of the internal structure of expansive soil induced by dry-wet cycles, AIP Advances 11(7)https://doi.org/10.1063/5.0057450\u003c/li\u003e\n\u003cli\u003eSun X, Li X, Mao T, et al(2021) Fracture evolution analysis of soil-rock mixture in contrast with soil by CT scanning under uniaxial compressive conditions, Science China Technological Sciences 64(12): 2771-2780.https://doi.org/10.1007/s11431-020-1888-9\u003c/li\u003e\n\u003cli\u003eZhao X, Li L, Yang B, et al(2022) Application of fractal to evaluate the drying shrinkage behavior of soil composites from recycled waste clay brick, Fractal, and Fractional 7(1): 25.https://doi.org/10.3390/fractalfract7010025\u003c/li\u003e\n\u003cli\u003eFu X, Ding H, Sheng Q, et al(2022) Fractal Analysis of Particle Distribution and Scale Effect in a Soil\u0026ndash;Rock Mixture, Fractal and Fractional 6(2): 120.https://doi.org/10.3390/fractalfract6020120\u003c/li\u003e\n\u003cli\u003eTang, Y.; Yang, B.; Zhao, X.; Yang, C(2023) Structural and Fractal Analysis of Soil Cracks Due to the Roots of Setaria, Viridis. Fractal Fract. https://doi.org/10.3390/fractalfract7010019\u003c/li\u003e\n\u003cli\u003eWu J, Yuan J, Ng C W W(2012) Theoretical and experimental study of the initial cracking mechanism of an expansive soil due to moisture-change, Journal of Central South University 19(5):1437-1446. https://doi.org/10.1007/s11771-012-1160-9\u003c/li\u003e\n\u003cli\u003eMenon S, Song X(2019) Coupled analysis of desiccation cracking in unsaturated soils through a non-local mathematical formulation, Geosciences 9(10): 428.https://doi.org/10.3390/geosciences9100428\u003c/li\u003e\n\u003cli\u003eLi G, Wang F, Ma W, et al(2018). Variations in strength and deformation of compacted loess exposed to wetting-drying and freeze-thaw cycles, Cold Regions Science and Technology 151:159-167.https://doi.org/10.1016/j.coldregions.2018.03.021\u003c/li\u003e\n\u003cli\u003eZhou Z, Ma W, Zhang S, et al(2018) Effect of freeze-thaw cycles in mechanical behaviors of frozen loess, Cold Regions Science and Technology 146: 9-18.https://doi.org/10.1016/j.coldregions.2017.11.011\u003c/li\u003e\n\u003cli\u003eFeng L, Zhang M, Jin Z, et al(2021) The genesis, development, and evolution of original vertical joints in loess, Earth-Science Reviews 214: 103526.https://doi.org/10.1016/j.earscirev.2021.103526\u003c/li\u003e\n\u003cli\u003eXu J, Hu K, Zhou L, et al(2023) Influence of wet-dry cycles on uniaxial compression behavior of fissured loess, Environmental Earth Sciences 82(1) : 5.https://doi.org/10.1007/s12665-022-10684-3\u003c/li\u003e\n\u003cli\u003eTang D, Deng L, Fan W, et al(2024) Extension mechanism and failure mode investigation on a fissured loess slope induced by loading, Bulletin of Engineering Geology and the Environment 83(7): 294. https://doi.org/10.1007/s10064-024-03787-7\u003c/li\u003e\n\u003cli\u003eAbbaszadeh M M, Houston S L, Zapata C E(2015) Influence of soil cracking on the soil-water characteristic curve of clay soil, Soils, and Rocks 38(1): 49-58.https://doi.org/10.28927/SR.381049\u003c/li\u003e\n\u003cli\u003eLi Z, Wang S, Jin L(2019) Experimental Study on the Effects of Coarse Particles on Cracking Behavior of Clay, Journal of Yangtze River Scientific Research Institute 36(6):99-105.https://doi.org/10.11988/ckyyb.20171218\u003c/li\u003e\n\u003cli\u003eZhong Y, Cai G, Zeng G(2022) The effect of initial water content and density on the swelling-shrinkage and cracking characteristics of compacted clay, Separations 9(12): 424.https://doi.org/10.3390/separations9120424\u003c/li\u003e\n\u003cli\u003eSchmidinger J, Schr\u0026ouml;ter I, B\u0026ouml;necke E, et al(2024) Effect of training sample size, sampling design and prediction model on soil mapping with proximal sensing data for precision liming, Precision Agriculture 25(3): 1529-1555. https://doi.org/10.1007/s11119-024-10122-3\u003c/li\u003e\n\u003cli\u003eLuo Z, Wang S, Zhang J, Yang Z ,et al(2020) Thickness effect on crack evolution of expansive soil, Chinese Journal of Geotechnical Engineering 42(10): 1922-1930.https://doi.org/10.11779/CJGE202010018\u003c/li\u003e\n\u003cli\u003eLiu J, Tang C, Zeng H, et al(2021) Evolution of desiccation cracking behavior of clays under drying-wetting cycles, Rock and Soil Mechanics 42(10): 2763-2772.https://doi.org/10.16285/j.rsm.2021.5459\u003c/li\u003e\n\u003cli\u003eTang C, Shi B, Liu C, et al(2008) Influencing factors of geometrical structure of surface shrinkage cracks in clayey soils, Engineering Geology, 101(3-4):204-217.https://doi.org/10.1016/j.enggeo.2008.05.005\u003c/li\u003e\n\u003cli\u003eTang C, Shi B, Cui Y(2018) Behaviors and mechanisms of desiccation cracking of soils, Chinese Journal of Geotechnical Engineering, 40(8):1415-1423.https://doi.org/10.11779/CJGE201808006\u003c/li\u003e\n\u003cli\u003eLu L, Fan H, Chen H, et al(2014) Influencing factors for uniaxial tensile strength of dispersive soils, Chinese Journal of Geotechnical Engineering 36(6):1160-1166.https://doi.org/10.11779/CJGE201406023\u003c/li\u003e\n\u003cli\u003eGan F, Hang X, Liu Y, Ma Y(2018) Physicochemical and Mineralogical Properties of Bentonites in South Jiangsu, China, Acta Pedologica Sinica 55(4):945-954.https://doi.org/10.11766/trxb201711240517\u003c/li\u003e\n\u003cli\u003eWang J, Huang S, Guo W,et al(2020) Experimental study on fracture toughness of a compacted clay using semi-circular bend specimen, Engineering Fracture Mechanics 224:106814.https://doi.org/10.1016/j.engfracmech.2019.106814\u003c/li\u003e\n\u003cli\u003eHallett P D, Newson T A(2001) A simple fracture mechanics approach for assessing ductile crack growth in soil, Soil Science Society of America Journal, 65(4):1083-1088.https://doi.org/10.2136/sssaj2001.6541083x\u003c/li\u003e\n\u003cli\u003eLecocq N, Vandewalle N(2023) Dynamics of crack opening in a one-dimensional desiccation experiment, Physica A: Statistical Mechanics and its Applications, 321(3): 431-441.https://doi.org/10.1016/S0378-4371(02)01538-8\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":"loess paleosols, loess; crack evolution, moisture content, dry density","lastPublishedDoi":"10.21203/rs.3.rs-5294720/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5294720/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe alternating loess and loess paleo-soil layers exhibit distinct water contraction cracking behavior in the loess region. Investigating these characteristics is essential for projects in loess areas. This study focused on Q\u003csub\u003e3\u003c/sub\u003e loess and loess samples, revealing the following key findings:(1) Cracking occurs in three stages: crack initiation, skeleton formation, and complete development. (2) Loess paleo-soil requires higher initial cracking water content than Q\u003csub\u003e3\u003c/sub\u003e loess. After crack development, the overall water content of paleosoil remains higher. (3) Cracks are wider but fewer in paleo-soil. The highest water content is at the specimen\u0026rsquo;s edge. (4) Initial water content affects crack rate (\u003cem\u003er\u003c/em\u003e), total crack length (\u003cem\u003eL\u003c/em\u003e), and average crack width (\u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e) in both loess and loess paleo-soil specimens. Conversely, initial dry density inhibits \u003cem\u003er\u003c/em\u003e and \u003cem\u003eL\u003c/em\u003e but promotes \u003cem\u003eD\u003c/em\u003e\u003csub\u003eav\u003c/sub\u003e. (5) The two modes of the presence of clay grains result in higher clay content loess paleosols having greater deformability and soil tensile strength than Q\u003csub\u003e3\u003c/sub\u003e loess. Deformation-induced tensile forces and soil tensile strength play distinct roles during early and late crack development. (6) Using fracture toughness, energy diffusion formulas, and the elasticity model, it is concluded that paleosol has a weaker ability to produce new cracks but better deformation performance compared to Q\u003csub\u003e3\u003c/sub\u003e loess.\u003c/p\u003e","manuscriptTitle":"Crack Evolution and its Quantitative Analysis on Unsaturated Loess and Paleosoil","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-31 08:19:59","doi":"10.21203/rs.3.rs-5294720/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":"000d0b0f-a44e-4c55-bc13-97489ce426c6","owner":[],"postedDate":"October 31st, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-11-25T02:38:57+00:00","versionOfRecord":[],"versionCreatedAt":"2024-10-31 08:19:59","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5294720","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5294720","identity":"rs-5294720","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}