Influence of cracks on loess collapse under heavy rainfall

Abstract

Collapse is one of the frequent geological disasters on the Loess Plateau, which seriously threatens the safety of people's life and property. Taking the typical loess collapse in Wangdonggou, Changwu County, China as the research object, the loess collapse model is established through the field geological investigation and laboratory tests. Based on the principle of fluid–solid coupling, the failure mechanism of collapse body with the different crack depth and crack width are numerically simulated by the finite element method to study the influence of cracks on loess collapse under the action of heavy rainfall. The results show that with the infiltration of rainfall, on the one hand, the self-weight of the collapse body increases, which causes the increase of shear stress at the slope foot. On the other hand, when rainwater seeps out from the slope surface, it generates the seepage force, resulting the increase of the overturning moment of the collapse body. When the crack depth gradually increases from 0 to 6.0 m, the tensile stress at the crack tip gradually increases, the trend of collapse body toppling towards the free face is more and more obvious, the plastic zone gradually expands from the slope foot to the crack tip, and the safety factor of the collapse body decreases from 1.135 to 0.958. With the increase of crack width, the gravity center of collapse body gradually moves outward, the soil deformation at the slope foot and crack tip gradually increases, and the stability of the collapse body continuously decreases. The failure process of toppling loess collapse includes tensile crack initiation, crack expansion and collapse body bending and toppling. The results reveal the influence of crack depth and crack width on the stability of the collapse body under the action of rainfall, as well as the instability failure mechanism of the collapse body, which can provide theoretical support for the prevention and control of collapse geological disasters and soil gravity erosion in Loess Plateau.