Assessing Slope Stability with an Improved 3D Numerical Manifold Method

A 3D stability analysis is essential in slope designs, since it is more in line with real situation, and can provide more reasonable results than a 2D analysis. A numerical model termed as ISR3DNMM-GPS method is proposed for factor-of-safety (FOS) calculation and 3D failure surface (or critical slip surface) determination involved in a 3D slope stability analysis. In the proposed numerical model, an improved strength reduction technique (ISRT) which can avoid unreasonable plastic zones appearing in the deep area of a slope is implemented into the 3D numerical manifold method (3DNMM), and an improved strength-reduction-based 3DNMM (ISR3DNMM) is developed. With the proposed ISR3DNMM, the FOS and generalized plastic strain (GPS) field corresponding to slope’s failure state can be obtained simultaneously. Then, a group of useful 3D points locating within the plastic zone of the slope are further determined based on the 3D slope’s GPS field. With these 3D points, an improved least square method is adopted to obtain a rational 3D failure surface, which passes through the slope’s weakest point. With the proposed ISR3DNMM-GPS method, the stability of two typical 3D slopes are analyzed. The numerical results indicate that 3D slopes’ stability can be effectively analyzed with the proposed numerical model. The proposed numerical model deserves further investigation.