New geometric restriction for the displacement-constraint points in discontinuous deformation analysis

A displacement-based seismic discontinuous deformation analysis (DDA) considers the influence of an earthquake by applying a time-dependent displacement constraint to simulate time-dependent ground movement of the base rock. However, unexpected variations of the base block stress and the block area in a seismic DDA may affect the block contacts with another block. This study theoretically clarifies the mechanism that causes unwanted base block distortion in a seismic DDA. A new geometric restriction is proposed for the assignment of displacement-constraint points to simulate the ground movement of two-dimensional (2D) and three-dimensional (3D) convex and concave blocks without changing the DDA algorithm. Additionally, the Daguangbao rock avalanche triggered by the Wenchuan earthquake in China is considered as a case study to demonstrate the capability of the new geometric restriction in a DDA to solve practical problems.