Sliding-Surface Analysis of Saturated Soil Slopes Under Variable Confining Pressure Using a Phase-Field Method

Seismic loading may increase confining pressure, which can degrade the soil shear modulus, alter the stress-field distribution within slopes, and thereby affect slope stability. In this study, a constitutive model relating shear modulus to confining pressure is developed within a phase-field framework based on the Günzburg–Landau equation. The proposed model establishes an exponential-type relationship among shear strain, confining pressure, and shear modulus and is intended to provide a unified description applicable to different soil types. Its applicability is validated through comparisons with published experimental data for sand and gravel under different confining pressures. The model is further applied to analyze the influence of confining pressure on the potential sliding surface of saturated soil slopes at the limit-equilibrium state.