3D Finite Element and Limit Equilibrium Modeling of the Initiation of Landslides

Large-scale failure of riverbank slopes containing sensitive clays can occur rapidly under undrained conditions. Field observations and numerical analyses indicate that forming a quasi-horizontal shear band can develop from the toe of the slopes and initiate a progressive type of failure. In this study, a semi-horizontal localization of the maximum shear strain is captured on three-dimensional slope models using RS3 finite element software. The analyses are stopped after initiating these semi-horizontal deformation patterns because no special regularization techniques are used to model strength degrading in the softening regime. Degrading the strength parameters, in general, makes the simulations pathologically mesh-dependent. In addition, developing semi-horizontal patterns results in numerical non-convergence, indicating the initiation of global instability as the safety factor becomes less than one. In this study, the formation of the semi-horizontal pattern of maximum shear strain is investigated for two different sizes of toe erosion models. In addition, slope stability analyses are carried out using 3D limit equilibrium software of Slide3D at the stages where the non-convergence takes place. The results are compared for different toe erosion models and different solution methods.