Influence of Raised Groundwater Level on the Stability of Unsaturated Soil Slopes

Abstract

The response of unsaturated soil slopes subjected to raised groundwater levels is generally governed by undrained shear strength. A series of unconsolidated undrained triaxial tests was conducted on reconstructed specimens of Xiashu loess with different water content. This can avoid the complexity involved with the measurement of matric suction. The Duncan-Chang hyperbolic model was modified to approximate the measured stress-strain responses. A correlation between water content and shear-strength parameters was established. The proposed model was then implemented in a finite-difference analysis program, against which two conventional calculations using the standard Mohr-Coulomb model with constant and varying soil properties with depth were compared. The analyses of an unsaturated soil slope subjected to raised groundwater levels demonstrate that soil properties should vary with water content; otherwise, an unsafe evaluation of slope stability will be obtained because the displacements of the slope may be underestimated if the dependency of water content is neglected.