Stability Analysis and Sustainable Cutoff Wall Parametric Optimization for Deep-Large Excavation High Slopes: A Case Study of the Yunnan Water Diversion Project

Slope stability analysis requires particular attention to groundwater effects, where seepage–stress coupling fundamentally alters mechanical responses. This investigation develops a field-calibrated numerical model using monitoring data from a water diversion project in Yunnan, using finite element analysis based on seepage–stress coupling theory. Comparative stability assessments through strength reduction methodology evaluate three scenarios: non-seepage conditions, seepage–stress interaction, and cutoff wall implementation. Results demonstrate the cutoff wall’s effectiveness, achieving optimal slope ratios of 1:1.41 compared to 1:2.21 under seepage–stress coupling. Parametric analyses reveal quantitative relationships between wall characteristics and stability metrics. Elastic modulus optimization within practical ranges (9362.63 MPa peak performance) enables steeper 1:1.37 slopes while maintaining safety factors. Strategic width reduction from 0.6 m to 0.4 m decreases concrete usage by 33% without compromising stability thresholds, proving cost-efficiency in large-scale applications. The methodology provides actionable guidelines for deep excavation projects facing similar hydrogeological challenges. Optimized cutoff walls enhance slope stability sustainably through ecological preservation and resource efficiency, providing actionable frameworks for eco-conscious geotechnical design aligned with global sustainability objectives.