Slope deformation due to drying-wetting cycles is a great concern in both the risk warning of slopes and the design of various slope structures on the slope. A new full-process slope deformation analysis method was derived based on slice methods, with innovations in terms of the constitutive equation, displacement compatibility equation, and stress equilibrium equation. A constitutive model of the soil was proposed with defined parameters, and it was reported to perform well in the prediction of the deformation increment and strength reduction due to drying-wetting cycles. The potential slip surface was shown to be a key component of characterizing the full-process deformation of a slope and to exhibit the displacement compatibility trend in which the relative horizontal displacement along the potential slip surface was equal at various locations. A slope deformation analysis algorithm was derived to analyze the shear deformation characteristics of potential slip surfaces and the volumetric deformation characteristics of sliding bodies subjected to drying-wetting cycles. The proposed method was validated by comparing the predicted slope deformation characteristics with centrifuge model test and field observation results under drying-wetting cycles. The method was confirmed to predict the full-process deformation of soil slopes during drying-wetting cycles, including the small deformation stage, prefailure stage, failure process and postfailure stage.

Slip zone soil, a crucial factor in landslide stability, is essential for understanding the initiation mechanisms and stability assessment of reservoir bank landslides. This study investigates the strength characteristics of slop zone soil under drying-wetting (D-W) cycles to inform research on reservoir bank landslides. As an illustration of this phenomenon, the Shilongmen landslide in the Three Gorges Reservoir serves as a case study. Taking into account the impact of both D-W cycles and the overlying load on the soil. the strength characteristics of the slip zone soil are investigated. Experimental results show that slip zone soil exhibits strain softening during D-W cycles, becoming more pronounced with more cycles. D-W cycles cause deterioration in shear strength and cohesion of slip zone soil, especially in the first four cycles, while the internal friction angle remains largely unchanged. The compaction effect of the overlying load mitigates the deterioration caused by D-W cycles. The findings reveal the weakening pattern of mechanical strength in slip zone soil under combined effects of overlying load and D-W cycles, offering valuable insights for studying mechanical properties of slip zone soil in reservoir bank landslides.

The strength of clay subject to drying-wetting cycles is influenced by multiple factors, rendering the prediction of its variation trend challenging. To investigate the variation in strength characteristics of cohesive soil subjected to drying-wetting cycles, silty clay was obtained from the Liangzhu archaeological site to prepare remolded soil sample. Subsequently, saturated consolidated undrained triaxial tests of control group, crack inhibition group, varied dry water content group and different overconsolidation ratio (OCR) group were carried out under different drying-wetting cycles. A thorough analysis of the test results reveals that the number of drying-wetting cycles does not affect the soil's critical state or phase transformation state. The strength of soil exposed to drying-wetting cycles is influenced by a combination of factors, including cracks formed during drying, overconsolidation, and hysteresis phenomenon. Specifically, cracks will destroy the integrity of the soil and thus reduce its strength, while overconsolidation and hysteresis contribute to an enhancement in soil strength. As the number of drying-wetting cycles increases, the prominence of cracks in the soil becomes more pronounced. Additionally, as the dry water content decreases, the deviatoric stress, excess pore water pressure, and effective stress path of soil continue to evolve in the direction of increasing OCR. This research enriches the study of the strength characteristics of clay under drying-wetting cycles, providing a foundation for the preventive protection of earthen sites in humid environments in geotechnical engineering.

Water level fluctuations in the reservoir deteriorate soils and rocks on the bank landslides by dryingwetting (D-W) cycles, which results in a significant decrease in mechanical properties. A comprehensive understanding of deterioration mechanism of sliding-zone soils is of great significance for interpreting the deformation behavior of landslides. However, quantitative investigation on the deterioration characteristics of soils considering the structural evolution under D-W cycles is still limited. Here, we carry out a series of laboratory tests to characterize the multi-scale deterioration of sliding-zone soils and reveal the mechanism of shear strength decay under D-W cycles. Firstly, we describe the micropores into five grades by scanning electron microscope and observe a critical change in porosity after the first three cycles. We categorize the mesoscale cracks into five classes using digital photography and observe a stepwise increase in crack area ratio. Secondly, we propose a shear strength decay model based on fractal theory which is verified by the results of consolidated undrained triaxial tests. Cohesion and friction angle of sliding-zone soils are found to show different decay patterns resulting from the staged evolution of structure. Then, structural deterioration processes including cementation destruction, pores expansion, aggregations decomposition, and clusters assembly are considered to occur to decay the shear strength differently. Finally, a three-stage deterioration mechanism associated with four structural deterioration processes is revealed, which helps to better interpret the intrinsic mechanism of shear strength decay. These findings provide the theoretical basis for the further accurate evaluation of reservoir landslides stability under water level fluctuations. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Binders can enhance soil properties and improve their suitability as subgrade fillers; however, the cementing effect and strength properties of solidified soil are highly susceptible to external environmental factors. This study evaluated the strength and durability of solidified sludge soil (PSCS) with varying binder (PSC) contents through unconfined compressive strength (UCS) tests combined with drying-wetting (D-W) and freezing-thawing (F-T) cycles, and identified the optimal binder content for performance enhancement. Additionally, mercury intrusion porosimetry (MIP) tests were conducted to analyze pore structure changes and explore the synergistic effects between hydration reactions and moisture variations induced by D-W/F-T cycles. Results indicate that binder content > 15 % significantly enhances PSCS strength and durability, with 15 % content (PSCS15) demonstrating the best economic advantage. During D-W/F-T cycles, the synergy between hydration reactions and moisture variations affects the pore structure, resulting in strength changes. For example, during D-W cycles, moisture movement causes the collapse of pores > 30 mu m, while hydration products fill the pores, decreasing the porosity of 5-30 mu m. Subsequently, moisture variations weaken the cementation effect, leading to a increase in the porosity of 5-30 mu m. This process causes the strength to fluctuate, showing a first decrease, followed by an increase, and then another decrease, with an overall reduction of 21.6 %. During the drying stage of D-W cycles, moisture evaporation inhibits hydration reactions in soil. In contrast, during F-T cycles, moisture remains in different physical states (e.g., solid ice crystals and liquid water). These moisture variations causing the collapse of pores >30 mu m, while hydration products fill the larger pores, increasing the porosity of 1-10 mu m. The strength first decreases and then increases, with an overall increase of 38.7 %. Furthermore, this study demonstrates that until the hydration process is completed, D-W cycles have a more significant negative impact on PSCS compared to F-T cycles.

Predisintegrated carbonaceous mudstone (PCM) that exhibits low strength and continuous disintegration is prone to wetting deformation after repeated seasonal rainfall. A reasonable assessment of wetting deformation is required to facilitate the settlement control of the PCM embankment when exposed to repeated rainfall. Herein, to reveal the wetting deformation mechanism of the PCM subjected to drying-wetting cycles, the effects of drying-wetting cycles on the wetting deformation characteristics of the PCM are investigated using the double-line method. Microscopic pore characteristics of the PCM under different drying-wetting cycles were analyzed through scanning electron microscope (SEM) micrographs. Comparative analysis of the wetting deformation data between the tests and the constitutive model considering the damage of drying-wetting cycles was carried out. The results showed that the deviator stress-strain relationship curves of the PCM exhibit the strain hardening without obvious peak and no strain softening phenomena. The critical wetting strain of the PCM was positively correlated with the number of drying-wetting cycles, while the critical deviator stress decreased with an increase in the number of drying-wetting cycles. As the number of cycles increased, the gelling material between the particles dissolved, the volume of pores inside the PCM increased, and the number of pores inside the PCM decreased. The porosity of PCM had a significant quadratic function with the number of drying-wetting cycles. A wetting deformation damage model was developed to calculate the wetting deformation of the PCM by considering the effects of drying-wetting cycles, which can be useful for evaluating rainfall-induced settlements of relevant engineering structures made from PCM.

In cold and saline soil areas, concretes usually experience multi-factor erosions, such as freezing- thawing cycles (FTCs), drying-wetting cycles (D-Ws), and salt erosion. To promote green and sustainable development of the construction industry, municipal solid waste incinerator bottom ash (MSWIBA) was adopted as a partial replacement for conventional fine aggregates in concretes. In this study, the coupled effects of the D-Ws and salt erosion (i.e., 5 % NaCl solution and 5 % Na2SO4 2 SO 4 solution) were experimentally conducted to investigate the mechanical and micro- structural properties of ordinary and MSWIBA concretes. The results showed that D-Ws had a negative effect on the mechanical properties of concretes. The depth and width of cracks in concretes increased with the D-Ws raised. During the D-Ws, the influence of salt solution on concretes could be divided into two stages. Initially, the filling effect of salt crystals was beneficial to the development of concrete strength. Subsequently, salt crystals accumulated in concretes caused cracks, and accelerated the deterioration of concrete specimens. Meanwhile, sodium sulphate reacted with hydration products in concretes to produce some expansive substances, the evident diffraction peaks of expansive substances (e.g., gypsum and ettringite) had been clearly observed after D-Ws. Thus, the damage effect of 5 % Na2SO4 2 SO 4 solution (SS) to concrete structure was more serious than that of water (WT) and 5 % NaCl solution (CS). Furthermore, the total porosity of the concrete specimens generally decreased with the MSWIBA substitution rate increased. There was an optimal MSWIBA content for concretes to obtain the excellent mechanical and microstructural properties. In detail, when the substitution rate of MSWIBA was between 0 % and 33.0 %, it had an excellent effect on improving the pore structure of concretes. Specifically, the compressive strength of concretes was larger than 35.0 MPa when the substitution rate of MSWIBA with natural river sand was between 24.8 % and 57.8 %, whereas the substitution rate of MSWIBA should not exceed 33.0 % exposed to D-Ws. This study could provide a significant reference for the sustainable development of concretes in cold and saline soil areas, as well optimization and innovation usage of MSWIBA.

The creep behavior of an expansive clay under undrained conditions is investigated considering the effects of freeze-thaw-drying-wetting (FTDW) cycles. Compacted specimens were subjected to 1, 4, and 10 FTDW treatments. Macroscopic changes were recorded and mercury intrusion porosimetry tests were conducted to reveal the expansive clay's structure evolution during the FTDW treatments. The undrained shear strength was first determined by the consolidated undrained shear tests for as-compacted specimens. Subsequently, saturated undrained creep tests under low confining pressure were performed at various deviator stress levels (D) to study the axial strain development with time for specimens subjected to different FTDW cycles (NFTDW). Experimental results show that 1) the macropores increase with the newly emerged peak at a diameter between 10 mu m to 20 mu m and micropores decrease after FTDW cycles; 2) the axial instantaneous strain (epsilon ai), creep strain (epsilon ac), and total strain (epsilon at) increase with FTDW cycles. The epsilon ai-D-NFTDW and epsilon at-D-NFTDW relationships of the specimens are distributed on a unique surface under a certain confining pressure level; 3) the axial strain rate decreases dramatically within the first 2,000 min and then remains nearly constant. Studies in this paper are valuable for advancing the understanding of the influences of environmental factors on the creep behavior of expansive clays.

Granite residual soil (GRS) exhibits favorable engineering properties in its natural state. However, a hot and rainy climate, combined with vibrations generated during mechanical construction, can cause a notable decrease in its strength. In this study, the evolution of stress-strain curves and strength parameters (cohesion c and internal friction angle phi), unconfined compression strength (UCS) under drying and wetting(DW) cycles and vibration were investigated by means of direct shear test and UCS test. Furthermore, modified formulas for calculating shear strength and UCS under DW cycles and vibration were proposed, and their accuracy was verified. The results are as follows: The stress-strain curve of shear strength exhibits strain-hardening characteristics, and the shear compressibility of the sample increases with the number of DW cycles and vibration time. However, the stress-strain curve of UCS shows strain-softening properties, and the peak strength shifts forward with the number of DW cycles and vibrations. With the increase in the number of DW cycles and the vibration time, c shows a non-linear degradation, with a maximum degradation of 58.6%. phi fluctuates and increases due to the densification effect of DW cycles, but the influence of vibration on phi decreases with the increase in the number of DW cycles. UCS rapidly decreases and gradually stabilizes after DW cycles and vibration, with a maximum degradation of 81.1%. This study can serve as a reference for the stability analysis of GRS pits subjected to long-term influences of hot and rainy climates and mechanical vibration, providing valuable insights for future research.