Study on slope failure criterion in strength reduction finite element method
ZHAO Shang-yi1, ZHENG Ying-ren1, ZHANG Yu-fang2 (1 Department of Civil Engineering, Logistical Engineering University, Chongqing 400041, China; 2 Shenzhen TieKe Geotechnical Engineering Co. Ltd., Shenzhen 518034, China)
Slope collapse and the slide body come into moving state from stable static state simultaneously, and are accompanied by a dramatic increase in displacement of slide body. Furthermore, the displacement is not a definite value, but an infinite increase. This is the definition of overall collapse of a slope. In finite element model, the slope reaches instability with the strength reduction, value of the nodal displacement just after slope failure has a sudden change compared to the one before failure. This actually means that no stress distribution can be achieved to satisfy both the yield criterion and global equilibrium. Slope failure and numerical non-convergence take place at the same time. An element stress reaching the yield criterion state not always means that infinite “plastic flow” occurred. It is determined by boundary condition. The plastic zone developed from slope toe to top not means the overall collapse occurred. On the other hand, the distribution of plastic zone was influenced by many factors such as Poisson's ratio, flow rule, etc. So non-convergence in finite element program can be taken as a suitable evaluating criterion of slope failure. Through a series of case studies, the applicability of the proposed method was clearly exhibited.