Stability of cement-red soil ecological substrate slope under simulated rainfall conditions: experiment and finite element analysis

Ecological slope protection offers a sustainable solution for mitigating rainfall-induced geotechnical failures. In this study, an ecological slope protection was constructed using an optimized ecological substrate composed of red soil, organic fertilizer, cement and wood chips in a 100: 20: 5: 15 ratio. SEM and EDS revealed that cement effectively anchors red soil, improving the stability of ecological substrate. To evaluate rainfall-induced performance, an artificial slope simulation (ASS) rainfall model with a cement-red soil ecological bag slope was developed, complemented by a small-scale finite element simulated slope (FESS) for cross-validation. The results demonstrated strong agreement between interlayer pressure measurements in the ASS and FESS numerical simulations, validating the high accuracy and feasibility of FESS. Based on the validated model, a full-scale ecological-bag slope protection FESS model was conducted on an actual slope to investigate the effects of rainfall intensity and slope gradient on stability. Under low rainfall intensity, slope gradient is the primary factor affecting the safety factor. However, increasing rainfall intensity reduces the safety factor through progressive matric suction loss. In the case study under the historical maximum rainfall intensity of 378 mm/12 h, the computed safety factor was 1.263, meeting the three-level slope safety requirements. Consequently, the optimized cement-red soil ecological substrate exhibits exceptional stability under extreme rainfall, providing a sustainable alternative to conventional slope protection systems and practical design guidelines for ecological slope engineering in rainfall-prone regions, contributing to enhanced geohazard mitigation.