To study the degree of strength parameter deterioration (DSPD) of Lushi swelling rock in the high slope area under wetting-drying cycles, 114 samples are remodeled. Wetting-drying cycle and triaxial tests are conducted to comprehensively analyze the influence of dry density, wetting-drying cycle path, and number of wetting-drying cycles on the strength deterioration characteristics of Lushi swelling rock. Using the fitting analysis and function superposition methods, the DSPD model of Lushi swelling rock under wetting-drying cycles is established, which considers the previous four influencing factors. The influence of the DSPD of Lushi swelling rock on the stability of high slopes under rainfall seepage and circulation conditions is studied. Lushi swelling rock exhibits significant strength deterioration characteristics under wetting-drying cycles. The overall DSPD for cohesion is higher than that of the internal friction angle. Under rainstorm conditions, strength deterioration leads to a shallower depth of the critical slip surface of the slope and a smaller safety factor. After eight rounds of rainfall seepage and circulation, the safety factor gradually decreases by approximately 14%-28%. This study provides and verifies the DSPD model of Lushi swelling rock under wetting-drying cycles, and the results could provide a basis for disaster prediction and the optimization design of swelling rock slopes.

Granite residual soils (GRS) are often encountered in geotechnical projects in the Guangdong-Hong Kong-Macao Greater Bay Area (briefly written as the Greater Bay Area, or abbreviated as GBA). The rea experiences frequent rainfall, leading to wetting-drying cycles that progressively diminish the shear strength of GRS. This weakening effect is not only significant but also accumulates, exhibiting a direct positive correlation with the number of cycles. Current studies on the soil strength attenuation due to wetting-drying cycles are typically limited to no more than 10 cycles, which is rather insufficient to uncover the long-term water-weakening behaviors and their accumulative impacts on GRS. To address this gap, typical GRS samples were first taken from the GBA and then prepared by making them go through a certain number of wetting-drying cycles (maximum of up to 100). Next, a total of 552 small- and large-scale direct shear tests were conducted to investigate the mechanisms of water-weakening effects on soil internal friction angle, cohesion, and shear strength. The degree of saturation and number of cycles were also examined to see their effects on the cumulation of water weakening. Based on results from the small-scale direct shear tests, a model was developed for assessing the weakening impact of water on soil strength. The accuracy of the model prediction was statistically evaluated. Last, the effectiveness and efficiency of the proposed model were demonstrated by validating against the results from the large-scale direct shear tests.

The treatment of excavated soil using the dry sieving method to produce recycled sand is an effective approach for resource utilization. Currently, the hot-air drying process used in this method exhibits high energy consumption. To address this issue, this study proposes a microwave drying technology to dry the excavated soil. Comparative experiments on microwave (1-6 kW) and hot-air (105-205 degrees C) drying of the excavated soil were conducted. The drying behavior and specific energy consumption of the excavated soil were investigated. The Weibull-Fick combined method was recommended for the segmental determination of the effective moisture diffusion coefficient, and the question of whether microwave drying adversely affects sand particles in the excavated soil was answered. The results revealed the following: Compared with hot-air drying, microwave drying demonstrated shorter drying time (3.5-38 min vs 75-1200 min), lower specific energy consumption (6.2-11.5 MJ/kg vs 22.3-55.4 MJ/kg), and a higher range of effective moisture diffusion coefficient (10-8-10-7 m2/s vs 10-9-10-8 m2/s). With increasing microwave power (3-6 kW), the time required for complete drying of the sample was reduced by up to 56 %. Under microwave drying, relaxing the termination moisture content criterion from 0 to 0.01 resulted in a 17 %-32 % reduction in specific energy consumption, accompanied by a 24 %-36 % decrease in drying time. Microwave drying did not damage sand particles within the excavated soil.

Silt soil is widely distributed in coastal, river, and lacustrine sedimentary zones, characterized by high water content, low bearing capacity, high compressibility, and low permeability, representing a typical bulk solid waste. Studies have shown that cement and ground granulated blast furnace slag (GGBFS) can significantly enhance the strength and durability of stabilized silt. However, potential variations due to groundwater fluctuations, long-term loading, or environmental erosion require further validation. This study comprehensively evaluates cement-slag composite stabilized silt as a sustainable subgrade material through integrated laboratory and field investigations. Laboratory tests analyzed unconfined compressive strength (UCS), seawater erosion resistance, and drying shrinkage characteristics. Field validation involved constructing a test with embedded sensors to monitor dynamic responses under 50% overloaded truck traffic (simulating 16-33 months of service) and environmental variations. Results indicate that slag incorporation markedly improved the material's anti-shrinkage performance and short-term erosion resistance. Under coupled heavy traffic loads and natural temperature-humidity fluctuations, the material exhibited standard-compliant dynamic responses, with no observed global damage to the pavement structure or surface fatigue damage under equivalent 16-33-month loading. The research confirms the long-term stability of cement-slag stabilized silt as a subgrade material under complex environmental conditions.

Improper anti-drainage treatment of weakly expansive soil subgrades can lead to significant post-construction deformation and uneven settlement, which severely affect the operational safety and service life of engineering projects. To comprehensively analyze the evolution of soil volume and strength under different hydraulic coupling paths during wetting-drying (W-D) cycles, a loaded W-D cycle testing device was developed. Soil volume was measured during the W-D cycles, and the shear strength and soil-water characteristic curves were analyzed after different cycles. The results indicate that during the W-D cycles, changes in soil volume and strength exhibited distinct stages with similar evolution characteristics. Under the investigated loading conditions, the soil demonstrated significant collapsibility during the wetting process, which gradually diminished as the number of cycles increased. Eventually, the W-D cycles caused the soil to reach an equilibrium state, where its swelling and shrinkage behavior became nearly elastic. At equilibrium state, there is a corresponding void ratio for any moisture content, which is the elastic void ratio (e0el). The e0el is irrespective of the number of cycles and initial dry density. Conversely, higher load and larger amplitude in W-D cycles tend to decrease the e0el. Furthermore, by correlating the unsaturated soil matric suction, secant modulus, and stress path, the volume evolution mechanism of the soil was analyzed based on the soil effective stress theory and pore evolution. The results of this study can serve as a crucial reference point for revealing the deformation mechanism of weakly expansive soil subgrades and selecting appropriate road settlement control methods.

The application of novel materials that enhance soil engineering properties while maintaining vegetation growth represents an innovative strategy for ecological protection engineering of expansive soil slopes. Laboratory tests, including wetting and drying cycle tests, direct shear tests, unconfined swelling ratio tests, and vegetation growth tests, were conducted to analyze the effects of xanthan gum on both engineering and vegetation-related properties of expansive soil. The feasibility of xanthan gum for soil improvement was systematically evaluated. The interaction mechanism between xanthan gum and expansive soil was elucidated through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. Results demonstrated that xanthan gum effectively inhibited crack development and strength loss. With increasing xanthan gum content, the crack area ratio decreased logarithmically by up to 58.62%, while cohesion increased by 82.96%. The unconfined swelling ratio exhibited a linear reduction, with a maximum decrease of 43.58%. Notably, xanthan gum accelerated seed germination rate but did not significantly affect long-term vegetation growth. Mechanistically, xanthan gum improved soil properties via two pathways: (1) forming bridging structures between soil particles to enhance cohesion and tensile strength; (2) filling soil voids and generating a polymer film to inhibit water-clay mineral interactions, thereby reducing hydration membrane thickness. These findings offer both theoretical insights and practical guidelines for applying xanthan gum in ecological protection engineering of expansive soil slopes.

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.

Biopolymer-fiber treated soil has great application potential in civil engineering with better mechanical properties and environmental sustainability. However, the durability and strength degradation rules of biopolymerfiber treated soil with different residual moisture content (RMC) values subjected to severe weathering cycles remain unclear. The effects of wetting-drying (W-D) and freezing-thawing (F-T) cycles on xanthan gum biopolymer-jute fiber treated soil (XJTS) with different RMC values are experimentally investigated. Particular emphasis is placed on mechanical strength characteristics, stress-strain behavior, failure patterns, and associated microstructural evolution encompassing pore structure modifications. The results show that when the RMC value of the XJTS material is higher, its mechanical strength is more affected by the F-T cycle. The effect of the W-D cycles on the pore size and distribution in the XJTS material was more significant than F-T cycles, and the percentage of microfissure (>100 mu m) increased from 6.76 % to 50.01 % after the 20th W-D cycle.

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.