Numerical Implementation of Three-Dimensional Nonlinear Strength Model of Soil and Its Application in Slope Stability Analysis

Abstract

Based on previous research results and the three-dimensional strength characteristics of different soil types, a three-dimensional nonlinear strength model of soil considering tenso-shear (T-S) coupling strength and compressive-shear (C-S) strength is established. The proposed model can better describe the influences of intermediate principal stress and T-S coupling stress in soil. The secondary development of user material subroutine (UMAT) is conducted in ABAQUS. The UMAT procedure is programmed using an implicit backward Euler integral algorithm, and numerical experiments verify its accuracy. This procedure is then applied to the analysis of slope stability. Using the strength reduction method, the stability of the saturated slope and unsaturated slope are analyzed. The numerical results show that when the slope approaches instability, the T-S coupling plastic zone and T-S coupling failure surface develop downward from the top surface of the slope. The critical slip surface is a composite slip surface composed of a C-S slip surface and a T-S coupling failure surface. Compared with the M-C strength model, the three-dimensional nonlinear strength model can describe the failure mechanism of the slope more clearly and reasonably and can provide an accurate stability evaluation.