Hao Li

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.

This study aims to convert waste rock into sustainable building materials by using it as coarse and fine aggregates to prepare basalt fiber and steel fiber-reinforced concrete (BFRC and SFRC). The optimal dosages and reinforcement mechanism of fibers were determined through mechanical performance tests, P-wave velocity tests, slump tests, and SEM analysis. Experimental research shows that incorporating an appropriate amount of fiber can improve the performance of concrete, and all BFRC and SFRC specimens meet the strength requirements. The concrete achieves the best strengths with 40 kg/m³ of steel fiber and 2 kg/m³ of basalt fiber. Compared to the control specimens, steel fiber greatly improves tensile strength by 22.2% and flexural strength by 27.4%, and basalt fiber increases them by 20.2% and 17.4%, respectively. Although SFRC specimens exhibit higher strengths, the production cost and CO₂ emissions of SFRC are significantly higher, with 2.46 times and 1.21 times than that of BFRC. SEM analysis revealed that the incorporation of an optimal dosage of fibers resulted in a denser microstructure within the concrete matrix. Basalt fiber and steel fiber with high elastic modulus and tensile strength provide significant bridging effects and crack resistance. The uniform distribution of fibers forms a dense network structure, limiting the generation and propagation of microcracks, thereby improving the mechanical properties. Overall, the addition of basalt fiber in waste rock concrete may be a more favorable choice. Besides, this study provides a theoretical basis for the resource utilization of waste rock and contributes to promoting the application of waste rock concrete in engineering.