New Instability Criterion for Stability Analysis of Homogeneous Slopes with Double Strength Reduction

A new instability criterion based on the critical slope concept and the double strength reduction is proposed to evaluate the stability of slopes. In this method, the critical slope contour is determined by the slip-line field theory with the reduced cohesion and the internal friction angle, and the slope reaches the limit equilibrium state when it intersects with the critical slope contour at the toe of the slope. The proposed method is validated against a published case and compared with the traditional instability criterion. In addition, the calculation results regarding four slope cases revealed that the reduction ratio of soil strength derived from the proposed method is more reasonable, and the comprehensive safety factor is equal to the polar diameter method. Thus, the proposed method can be adopted to quantify the instability criterion.