Investigation of the Role of Crown Crack in Cohesive Soil Slope and Its Effect on Slope Stability Based on Extended Finite Element Method

Tensile cracks in soil slopes, especially developing at the crown, have been increasingly recognized as the signal of slope metastability. In this paper, the role of crown cracks in natural soil slopes was investigated and its effect on stability was studied. A numerical modeling of slope and simulation of tensile behavior of soil, based on the Extended Finite Element Method (XFEM), was used. A numerical soil tensile test was applied to validate the use of XFEM on tensile behavior of soil before the simulation. Slope failure was simulated by using the Strength Reduction Method, which determines the potential slip surface of slope. The simulation results indicate forming of crown crack in natural soil slopes when the plastic zone starts penetrating. Therefore, it is reasonable to consider the crown crack as the signal of slope metastability. A sensitivity analysis shows the effect of cracking on slope stability if cracks are at the position of the tension zone. The stress variation analysis, from the surface slip deformation, reveals that the slope is at a state of compressive stress. When plastic zone starts penetrating, the upper part of slope generates tension zone, but the extent of tension zone is restricted by the slope failure. This suggests why tensile cracks are difficult to form and stretch in the deep part of the slope. The implementation of XFEM on slope stability analysis can be used for assessing the tensile strength of soil and forecasting the time of slope failure related disaster.