Effects of seismic force and pore water pressure on stability of 3D unsaturated hillslopes

Three-dimensional (3D) kinematic limit analysis of unsaturated hillslopes is presented in this paper. Different from the traditional two-dimensional (2D) mechanism based on the infinite slope model, the 3D failure mechanism is more rational for its advantage in taking the out-of-plane geometries and soil properties into consideration. The soils in engineering practice are mostly unsaturated in nature and are commonly characterized with an arbitrary distribution of the moisture content, i.e., the matric suction, and therefore the formation of the work balance equation becomes much more elaborated using traditional methods. To tackle the nonlinear features of matric suction, a semi-analytical method is presented and is validated through comparisons with the benchmark solutions. The hillslope stability under seismic and pore water pressure conditions are both numerically studied. The results are presented in forms of graphs for a practical range of parameters, indicating the significance in accounting for the influences of 3D constraints, seismic loads and pore water pressures in hillslope stability assessments.