DDA modeling of the seismic response of large rock cavern complex

摘要

The discontinuous deformations analysis (DDA) method calculates large deformations and discontinuousrnproblems using time-step solving, and provides an effective tool to analysis the seismic dynamicrnresponse of the rock mass engineering. In this paper, some investigations for the DDA modeling of the seismicrnresponse of large rock cavern complex are carried out. First, the existing seismic input methods includingrnthe multi-blocks Newmark method, large mass method and large stiffness method are implemented in thernDDA program, and the applicability of these methods are discussed. Second, considering the characteristic ofrnthe seismic response of large rock cavern complex, a new DDA modeling including a coupling model and arnforce input method is presented, and can guarantee that the scattered waves are absorbed at both the bottomrnboundary and the lateral boundaries. Last, the modified DDA program with the new modeling is used for arncase study. Simulations of the quasi-static and the seismic dynamic stages for the large rock cavern complexrnof the Dagangshan hydropower station in Southwest China are carried out. Considering the stress and the displacementrnafter the sequential excavation, the most unfavorable movable blocks are found. Under the strongrnearthquake, seismic response of the large rock cavern complex can be visually divided into four phases, seriousrndamage of the main machine building and local damage of the downstream side wall of the main transformerrnchamber are observed, and it is proposed that failures of the most unfavorable movable blocks is anrnearly sign of collapse of the rock cavern complex.