Extension of the Discontinuous Deformation Analysis Method to Simulate Seismic Response of a Large Rock Cavern Complex

Abstract

The discontinuous deformation analysis (DDA) method calculates large deformations and discontinuous problems using time-step solving and provides an effective tool for analyzing the seismic response of rock mass engineering. In this paper, extensions of the DDA method to simulate the seismic response of a large rock cavern complex are carried out. First, applicability of the existing seismic input methods, including the multiblock Newmark method, large mass method, and large stiffness method, are discussed. Second, considering the characteristics of the seismic response of a large rock cavern complex, a new seismic DDA model that includes a coupling model and a force-input method is presented. Last, the extended DDA method is used for a case study. Simulations of the quasi-static and seismic dynamic stages for the large rock cavern complex of the Dagangshan hydropower station in southwest China are carried out. Considering the stress and displacement distributions in the quasi-static stage, the most unfavorable movable blocks are found. In the seismic dynamic stage, serious damage to the main machine building and local damage of the downstream sidewall of the main transformer chamber are observed, and the seismic response of the large rock cavern complex can be visually divided into four phases, which show that failures of the most unfavorable movable blocks are an early sign of collapse of a rock cavern complex.