Evolution and Influencing Mechanisms of the Yili Loess Mechanical Properties under Combined Wetting-Drying and Freeze-Thaw Cycling

Zhang, Yongliang; Zhang, Zizhao; Hu, W. Z.; Zhang, Yanyang

doi:10.3390/ma16134727

Cited by 6 publications

(4 citation statements)

References 15 publications

(15 reference statements)

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“…Therefore, β is 0 • ; L is the tensile strength of the roots. The effect of root content can be analyzed by Equation (5).…”

Section: Theoretical Results Of the Shear Strength Of Samples Under F...mentioning

confidence: 99%

“…Freeze-thaw cycles change the mechanical properties and structural characteristics of soils [3][4][5][6][7] and lead to soil deformation. A study on the physical properties of soils amid freeze-thaw cycles fundamentally emphasized the impact of two variables: the number of freeze-thaw cycles and the initial moisture content on soil shear strength.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Freeze–Thaw Cycles on the Shear Strength of Root-Soil Composite

Liu,

Huang,

Zhang

et al. 2024

Materials

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A large alpine meadow in a seasonal permafrost zone exists in the west of Sichuan, which belongs to a part of the Qinghai–Tibet Plateau, China. Due to the extreme climates and repeated freeze–thaw cycling, resulting in a diminishment in soil shear strength, disasters occur frequently. Plant roots increase the complexity of the soil freeze–thaw strength problem. This study applied the freeze–thaw cycle and direct shear tests to investigate the change in the shear strength of root-soil composite under freeze–thaw cycles. This study examined how freeze–thaw cycles and initial moisture content affect the shear strength of two sorts of soil: uncovered soil and root-soil composite. By analyzing the test information, the analysts created numerical conditions to foresee the shear quality of both sorts of soil under shifting freeze–thaw times and starting moisture levels. The results showed that: (1) Compared to the bare soil, the root-soil composite was less affected by freeze–thaw cycles in the early stage, and the shear strength of both sorts of soil was stabilized after 3–5 freeze–thaw cycles. (2) The cohesion of bare soil decreased more than that of root-soil composite with increasing moisture content. However, freeze–thaw cycles primarily influence soil cohesion more than the internal friction angle. The cohesion modification leads to changes in shear quality for both uncovered soil and root-soil composite. (3) The fitting equations obtained via experiments were used to simulate direct shear tests. The numerical results are compared with the experimental data. The difference in the soil cohesion and root-soil composite cohesion between the experiment data and the simulated result is 8.2% and 17.2%, respectively, which indicates the feasibility of the fitting equations applied to the numerical simulation of the soil and root-soil composite under the freeze–thaw process. The findings give potential applications on engineering and disaster prevention in alpine regions.

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“…Therefore, β is 0 • ; L is the tensile strength of the roots. The effect of root content can be analyzed by Equation (5).…”

Section: Theoretical Results Of the Shear Strength Of Samples Under F...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Freeze–Thaw Cycles on the Shear Strength of Root-Soil Composite

Liu,

Huang,

Zhang

et al. 2024

Materials

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“…The impact of coupled WD-FT cycling on soil cohesion was determined by the superposition effect of the two. Therefore, the degree of soil damage and cohesion decreased the most in coupled WD-FT cycling [31,32] As shown in Figure 22, the impact of coupled WD-FT cycling on soil strength was the most significant, observed by way of WD cycling, while FT cycling had the least impact. The best effect of all three occurred at the time of the first cycle, i.e., the first wet-dry, freeze-thaw, and coupled wet-dry and freeze-thaw cycles had the greatest effect on the mechanical characteristics of the soils.…”

Section: Shear Strength Evolution and Attenuation Trendsmentioning

confidence: 93%

Shear Strength of Loess in the Yili Region and Corresponding Degradation Mechanisms under Different Cycling Modes

Zhang,

et al. 2023

Water

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In the Yili region, China, complex environmental conditions induce repeated wet–dry (WD) and freeze–thaw (FT) cycles, deteriorating soil shear strength and producing frequent loess landslides. In this study, we collected soil samples from the Alemale landslide, Yili Prefecture and performed their triaxial shear tests with different numbers of WD, FT, and WD-FT cycles. In addition, we summarized the change mechanisms of loess mechanical properties and its deterioration, in the Yili region, under different cyclic effects. Subsequently, the test results under the three cycling modes were compared and analyzed, the differences in the deterioration effects of different cyclic conditions on loess were discussed in depth, and finally, a multiple linear regression model was established and the weights of single factors under the action of coupled cycles were analyzed. The results show the following: (1) Regardless of the confining pressure values, the principal stress evolution trends in soil samples under different cycling modes were generally consistent, i.e., after an initial increase, peak values were reached, followed by a final decline. (2) Under unconsolidated undrained (UU) conditions, shear strength values of all soil samples tested under the three cycling modes dropped after the first twenty cycles, exhibiting different evolution patterns. (3) Coupled WD-FT cycling most significantly promoted soil shear strength degradation, with less WD cycling effect, and FT cycling had the least significant effect; in all three modes, the first cycle had the highest contribution to this effect. From the perspectives of cohesion, angle of internal friction, and decay of shear strength attenuation, the coupled WD-FT cycling effect on soil shear strength could not be reduced to a simple single-factor addition–subtraction relationship. (4) Weight analysis of soil samples after WD, FT, and WD-FT cycling revealed that WD cycles in the coupled WD-FT cycling mode had the most significant impact on the shear strength attenuation of soil samples (contributing 57%), FT cycles had a medium impact (contributing about 33%), while the effect of the total number of cycles was negligible (about 10%). The research results provide experimental and theoretical bases for subsequent control of loess landslides.

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“…Due to the migration of water and salt, the salinity distribution in practical engineering is quite different, which causes enormous harm to large-scale water diversion projects, such as canals and slopes etc. [22][23][24][25][26][27]. At present, there are many studies on the loess in the monsoon area in the reports [28][29][30][31], and the research on Ili loess mainly focuses on the mechanical properties under cycling test conditions of dry-wet [32,33] and freeze-thaw [34,35], respectively.…”

Section: Introductionmentioning

confidence: 99%

Study on the Unified Mechanical Properties of Ili Undisturbed Loess under the Influence of Soluble Salt

Niu,

Zhao

et al. 2023

Sustainability

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Through three stress path tests of unsaturated Ili undisturbed loess, the effect of soluble salt content on the deformation of net mean stress, suction, and deviated stress were investigated. The mechanical properties of the normalized compression curve, soil water characteristic curve and critical state line were revealed. The test results indicate that: in the isotropic compression test, the normal compression curves controlling different suctions can be characterized by using the initial void ratio and the yield net mean stress, and can be described as a two-parameter exponential function. In the triaxial shrinkage test, the soil water characteristic curves controlling vary net mean stresses are dimensionless by using saturated moisture and air entry value, and the normalization formula can be characterized by a single parameter exponential function. In the consolidation shear test, the corresponding effective net mean stress is calculated by suction and saturation. The critical state lines under the unsaturated condition controlling vary suctions can be described as the critical state line under the saturated condition on the plane of effective net mean stress and deviator stress. When the effective net mean stress is constant, the critical state lines under the unsaturated condition can be characterized by the degree of gas saturation and the ratio of unsaturated void ratio to saturated void ratio. The research will offer reference pointing at the regulation and utilization of water and salt in the loess region of Central Asia, so as to better guarantee the sustainable development of saline-alkali land project construction.

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Evolution and Influencing Mechanisms of the Yili Loess Mechanical Properties under Combined Wetting-Drying and Freeze-Thaw Cycling

Cited by 6 publications

References 15 publications

Effect of Freeze–Thaw Cycles on the Shear Strength of Root-Soil Composite

Effect of Freeze–Thaw Cycles on the Shear Strength of Root-Soil Composite

Shear Strength of Loess in the Yili Region and Corresponding Degradation Mechanisms under Different Cycling Modes

Study on the Unified Mechanical Properties of Ili Undisturbed Loess under the Influence of Soluble Salt

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