Different contributions of two shear strength parameters to soil slope stability with limit equilibrium method based slice techniques

This paper presents the different contributions of two shear strength parameters to the factor of safety (FOS) value in limit equilibrium method (LEM)-based slice techniques. Many potential slip surfaces are designed and evaluated for their FOS values with respect to the slip depth in a homogeneous soil slope. This paper found that FOS values contributed only by internal cohesion decrease rapidly and inversely as the slip depth increases. However, FOS values contributed only by internal friction angle increase slowly and linearly as the slip depth increases. Because of the different contributions of cohesion and internal friction angle to slope stability, FOS values decrease and then increase with respect to the slip depth, allowing it to have a minimum value at an intermediate depth. This is the mechanical reason for the existence of a critical slip surface with a minimum FOS value in LEM-based slice techniques in slope stability assessment. Further evaluation of an actual slope shows that these findings are also valid to the presence of groundwater and soil inhomogeneity.