Evolution of mechanical behaviours of an expansive soil during drying-wetting, freeze–thaw, and drying-wetting-freeze–thaw cycles

Zhao, Guangxin; Han, Zhong; Zou, Wenming; Wang, Xie-qun

doi:10.1007/s10064-021-02417-w

Cited by 43 publications

(20 citation statements)

References 72 publications

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“…This study shows that with the increase in the number of drying–wetting cycles, the average pore size and porosity in the soil gradually increase as well. This is consistent with the results obtained by Zhao et al [ 42 ]. The average pore diameter and porosity of expansive soil were reduced by 37% and 30%, respectively, which may be caused by the interaction of mineral components in coal gangue and expansive soil.…”

Section: Discussionsupporting

confidence: 94%

Study on Crack Development and Micro-Pore Mechanism of Expansive Soil Improved by Coal Gangue under Drying–Wetting Cycles

Zhu

Zhang

et al. 2021

Materials

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Expansive soil is prone to cracks under a drying–wetting cycle environment, which brings many disasters to road engineering. The main purpose of this study is use coal gangue powder to improve expansive soil, in order to reduce its cracks and further explore its micro-pore mechanism. The drying–wetting cycles test is carried out on the soil sample, and the crack parameters of the soil sample are obtained by Matlab and Image J software. The roughness and micro-pore characteristics of the soil samples are revealed by means of the Laser confocal 3D microscope and Mercury intrusion meter. The results show that coal gangue powder reduces the crack area ratio of expansive soil by 48.9%, and the crack initiation time is delayed by at least 60 min. Coal gangue powder can increase the internal roughness of expansive soil. The greater the roughness of the soil, the less cracks in the soil. After six drying–wetting cycles, the porosity and average pore diameter of the improved and expanded soil are reduced by 37% and 30%, respectively, as compared to the plain expansive soil. By analyzing the cumulative pore volume and cumulative pore density parameters of soil samples, it is found that the macro-cracks are caused by the continuous connection and fusion of micro-voids in soil. Coal gangue powder can significantly reduce the proportion of micro-voids, cumulative pore volume, and cumulative pore density in expansive soil, so as to reduce the macro-cracks.

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Section: Discussionsupporting

confidence: 94%

Study on Crack Development and Micro-Pore Mechanism of Expansive Soil Improved by Coal Gangue under Drying–Wetting Cycles

Zhu

Zhang

et al. 2021

Materials

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“…The sand fraction decreased by (3.9%) during the first nine cycles and then subsequently stabilized (±0.3%). The stabilization of particle group changes induced by wetting-drying cycles took longer than that of freezethaw cycles, mainly because of their different physical processes [38]. The fragmentation, denudation, dissolution-reprecipitation and aggregation occur during the wetting-drying cycles [11,31,34], while the freeze-thaw cycle process mainly involves fragmentation [33,39].…”

Section: Wetting-drying Cyclesmentioning

confidence: 99%

Effect of Freeze–Thaw and Wetting–Drying Cycles on the Hydraulic Conductivity of Modified Tailings

Meng,

Xia,

Xia

et al. 2024

Geosciences

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Mine tailings have shown viability as the fine–grained layer in a capillary barrier structure for controlling acid mine drainage in a circular economy. Their saturated hydraulic conductivities (ksat) under wetting–drying cycles and freeze–thaw cycles remain unexplored. In this study, modified tailings with a weight ratio of 95:5 (tailings/hydrodesulfurization (HDS) clay from waste–water treatment) and an initial water content of 12% were used. The ksat of specimens was measured after up to 15 wetting–drying cycles, each lasting 24 h, with a drying temperature of 105 °C. The ksat for wetting–drying cycles decreased from 3.9 × 10−6 m/s to 9.5 × 10−7 m/s in the first three cycles and then stabilized in the subsequent wetting–drying cycles (i.e., 5.7 × 10−7 m/s–6.3 × 10−7 m/s). Increased fine particles due to particle breakage are the primary mechanism for the ksat trend. In addition, the migration of fines and their preferential deposition near the pore throat area may also promote this decreasing trend through the shrinking and potentially clogging–up of pore throats. This could be explained by the movement of the meniscus, increased salinity, and, subsequently, the shrinkage of the electrical diffuse layer during the drying cycle. Similar specimens were tested to measure ksat under up to 15 freeze–thaw cycles with temperatures circling between −20 °C and 20 °C at 12 h intervals. Compared to the untreated specimen (i.e., 3.8 × 10−6 m/s), the ksat after three freeze–thaw cycles decreased by 77.6% (i.e., 8.5 × 10−7 m/s) and then remained almost unchanged (i.e., 5.6 × 10−7 m/s–8.9 × 10−7 m/s) in subsequent freeze–thaw cycles. The increased fine grain content (i.e., 3.1%) can be used to explain the decreased ksat trend. Moreover, the migration of fines toward the pore throat area, driven by the advancing and receding of ice lens fronts and subsequent deposition at the pore throat, may also contribute to this trend.

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“…Water 2023, 15 During the continuous humidification and dehumidification of soil samples in WD cycling, the internal particles underwent a cycle state of water absorption expansion-water loss contraction. In this state, some of the hydrophilic minerals between the soil particles departed from the status quo, decreasing the binding forces between the soil particles and reducing the soil cohesion to a certain extent.…”

Section: Shear Strength Attenuation Mechanism Of Wd Cycling (1) Atten...mentioning

confidence: 99%

“…After breaking the coupling force of soil particles, the particles sink under the action of gravity. After rearranging, the soil pores grow and the size and spacing among soil particles become more uniform [14][15][16]. The evolution trends of loess mechanical properties under different cycling modes have been investigated from different perspectives.…”

Section: Introductionmentioning

confidence: 99%

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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Evolution of mechanical behaviours of an expansive soil during drying-wetting, freeze–thaw, and drying-wetting-freeze–thaw cycles

Cited by 43 publications

References 72 publications

Study on Crack Development and Micro-Pore Mechanism of Expansive Soil Improved by Coal Gangue under Drying–Wetting Cycles

Study on Crack Development and Micro-Pore Mechanism of Expansive Soil Improved by Coal Gangue under Drying–Wetting Cycles

Effect of Freeze–Thaw and Wetting–Drying Cycles on the Hydraulic Conductivity of Modified Tailings

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

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