Yi Luo

Reliable characterization of freeze–thaw-induced structural change is essential for evaluating compacted soils used in cold-region engineering, where repeated freezing and thawing can alter both surface integrity and internal pore structure. This study combines digital imaging, quantitative crack analysis, and X-ray computed tomography to characterize structural changes in compacted expansive soil subjected to 0, 1, 4, 7, and 10 freeze–thaw cycles. Specimens with initial water contents of 18% and 25% were observed during freezing and after thawing, while the post-thaw three-dimensional pore structure of the 18% specimen was reconstructed from CT images. The 18% surface specimen exhibited no continuous crack network despite evident internal pore restructuring, whereas the 25% specimen showed pronounced crack opening during freezing and partial closure after thawing. With increasing cycles, the crack pattern evolved from a dominant wide crack to a branched network of narrower cracks and then became less continuous. CT-resolvable porosity increased from 23.0% initially to 26.7% after four cycles and then remained nearly stable, whereas connected porosity increased to 25.4% after ten cycles. These complementary observations indicate that post-thaw surface appearance alone may underestimate freeze–thaw-induced structural disturbance and highlight the importance of moisture condition and early-cycle evolution in cold-region engineering.

Landslide dams, as a special type of earth dams, are characterized by complex geomorphological features and geotechnical properties. The failure of landslide dams induced by seepage should not be overlooked. This study introduces a calculation method for analyzing the slope stability of landslide dams with three different material compositions under seepage conditions. Furthermore, the influence of spatial heterogeneity in particle size on the stability of landslide dam slopes subjected to unsaturated seepage is investigated using the random finite element method combined with Monte Carlo simulation. This paper provides a reference for the reliability evaluation of landslide dams with different material types.

Rainfall-induced failures in red clay slopes are common, yet the coupled influence of soil structure degradation and rainfall temporal patterns on slope hydromechanical behavior remains poorly understood. This study advances the understanding by investigating a cut slope failure in Yunnan through integrated field monitoring, laboratory testing, and numerical modeling. Key advancements include: (1) elucidating the coupled effect of structure degradation on both shear strength reduction and hydraulic conductivity alteration; (2) systematically quantifying the impact of rainfall temporal patterns beyond total rainfall; and (3) providing a mechanistic explanation for the critical role of early-peak rainfall. Mechanical and hydrological parameters were obtained from intact and remolded samples, with soil-water retention estimated via pedotransfer functions. A hydro-mechanical finite element model of the slope was constructed and calibrated using recorded rainfall, displacement data and failure surface. Six simulation scenarios were designed by combining three strength conditions (intact at natural water content, intact at saturation, remolded at natural water content) with two hydraulic conductivity values (intact vs. remolded). Additionally, four synthetic rainfall patterns, including uniform, peak-increasing, peak-decaying and bell-shaped rainfall, were simulated to evaluate their influence on pore water pressure development and slope stability. Results show remolding reduced hydraulic conductivity 4.7-fold, slowing wetting front advance and increasing shallow pore water pressure. Intact soil facilitated deeper drainage, elevating pressure near the soil-rock interface. Strength reduction induced by structure degradation (water saturating and remolding) enlarged the slope deformation zone by 1.5 times under same hydraulic conductivity. Simulations using saturated intact strength best matched field observations. The results from this specific slope indicate that strength parameters primarily control stability, while permeability affects deformation depth. Simulations considering different rainfall patterns indicate that slope stability depends more critically on the temporal distribution of rainfall intensity than on the total amount. Overall, peak-decaying rainfall led to the most rapid rise in pore water pressure, earliest instability and lowest failure rainfall threshold, whereas peak-increasing rainfall showed the opposite trends. Our findings outline a practical framework for assessing red clay slope stability during rainfall. This framework recommends using saturated intact strength parameters in stability analysis. It highlights the important influence of rainfall temporal patterns, especially those with an early peak, on failure timing and rainfall threshold.

The analysis of rainfall-induced landslides, which involve complex interactions between hydrology, soil mechanics, and geometry, is still limited by simplifying assumptions in existing models. We introduced a numerical model that couples soil infiltration with three-dimensional (3D) slope stability analysis. After validating against benchmark problems, we used this model to investigate the effects of various hydro-geotechnical conditions on slope stability. The results show that rainfall intensity dictates the stability of shallow landslides, while for deep-seated landslides, it governs the rate of progression toward failure. A high initial groundwater table reduces slope stability by accelerating soil weakening, particularly for deep landslides. Although upward moisture redistribution via matric suction is possible, its effect is negligible during infiltration, allowing deep saturation and landslide risk to persist. Furthermore, a low-permeability basal layer impedes drainage, leading to pore pressure buildup and a rapid decline in stability. The proposed model could potentially overcome the limitations in predictive accuracy of current hydro-geotechnical models arising from their oversimplified representations.

Slope instability may cause severe casualties, property losses, and ecological damage. To accurately evaluate slope stability grades and mitigate geological hazards, a dynamic stability assessment method based on variable weight theory and trapezoidal cloud model is proposed. First, an evaluation index system for slope stability is established following the principles of uniqueness, purposefulness, and scientific validity. Then, to improve the accuracy of subjective constant weights, the intuitionistic fuzzy analytic hierarchy process (IFAHP) is employed to calculate subjective constant weights. Considering the contrast intensity and conflict among indicators, an improved CRITIC method is applied to determine objective constant weights. To balance subjective and objective factors and avoid constant weight imbalance, the optimal comprehensive constant weights are computed based on game theory, effectively reducing bias caused by single weighting methods. Furthermore, to fully account for the influence of indicator state values on their weights, variable weight theory is introduced to dynamically adjust the comprehensive constant weights. Finally, based on the variable weights of evaluation indicators, a trapezoidal cloud model is utilized to construct the slope stability evaluation model, which is validated through an engineering case study. The results indicate that the stability grade of Stage 1 is assessed as basically stable, while Stages 2 and 3 are evaluated as stable. Numerical simulations show the safety factors of the three stages are 1.36, 1.83, and 2.36, respectively, verifying the correctness of the proposed model. The proposed model demonstrates practical engineering value in slope stability assessment and can be referenced for slope reinforcement and hazard prevention in later stages.

Enzyme-Induced Calcium Carbonate Precipitation (EICP) shows promise for desertification control. This study investigates the effects of solid-to-liquid ratio, calcium sources, Ca²⁺ concentration, temperature, enzyme-to-liquid ratio (ELR), and pH on the activity of soybean crude urease (SCU). Furthermore, the impact of EICP treatment cycles on the mechanical properties, compressive behavior, and wind erosion resistance of aeolian sand (AS) was systematically evaluated, with microstructural evolution and pore characteristics of cemented specimens analyzed through SEM and X-CT. Key findings reveal that SCU activity and the calcium carbonate precipitation rate (PR) reached optimal levels (80~99%) under conditions of a 1:10 solid-to-liquid ratio, 1.0~1.5 M CaCl₂ concentration, 35~70 °C temperature range, and pH 7. After seven EICP treatments, AS specimens exhibited complete cementation with an unconfined compressive strength (UCS) of 580 kPa and a reduced wind erosion rate of 0.151 g/min, effectively mitigating desertification. SEM and X-CT analyses confirmed significant pore infilling and bridging between particles, accompanied by a reduction in pore quantity and permeability coefficient by over two orders of magnitude. EICP demonstrates notable advantages in enhancing mechanical performance, environmental compatibility, and cost efficiency, positioning cemented AS as a viable construction material while offering insights for sand stabilization engineering. These findings provide essential technical support for material innovation, wind and sand disaster prevention, and the sustainable construction of desert highway bases and subbases.

Climate‐induced desiccation cracks exhibit a hysteresis behavior, referred to as crack dynamic hysteresis (CDH), where they display different geometric characteristics during the drying and wetting phases at constant soil water content. This phenomenon has a complex effect on slope stability, an aspect often overlooked in analytical and numerical methods. In this study, we conducted experimental and numerical analyses to provide new insights into the effects of the CDH on slope stability. A series of laboratory experiments on desiccation cracking under drying‐wetting cycles were performed. The testing results were used to develop and validate an extended dynamic dual‐permeability model. The proposed model was integrated into a set of slope stability analyses using the finite element method. The numerical model results show that CDH causes greater fluctuations in crack dynamics and increases soil water retention under drying‐wetting cycles. Neglecting this phenomenon leads to underestimation of slope stability during dry conditions and overestimation during wet conditions, with these discrepancies becoming more pronounced as the cycles progress. Furthermore, CDH changes the mechanical properties of soil, transitioning relatively stable zones to regions prone to localized instability. These unstable zones present significant challenges for accurately analyzing and managing slopes with cracked soil layers. Monitoring groundwater fluctuations and local crack development after heavy rainfall events is essential for mitigating localized slope collapses.

Desiccation cracks exhibit a hysteresis behavior, referred to as crack dynamic hysteresis (CDH), where they display different geometric characteristics during the drying and wetting phases at constant soil water content. CDH has a complex effect on slope stability, an aspect often overlooked in analytical and numerical methods. In this study, we conducted experimental and numerical analyses to provide new insights into the effects of CDH on slope stability. A series of laboratory experiments on desiccation cracking under D-W cycles were performed. The testing results were used to develop and validate an extended dynamic dual-permeability model (DDPM). The proposed DDPM was integrated into a set of slope stability analyses using the finite element method. The numerical model findings show that CDH causes greater fluctuations in crack dynamics and increases soil water retention under D-W cycles. Neglecting CDH leads to underestimations of slope stability during dry conditions and overestimations during wet conditions.