Xiaodong Fu

Study on elastic P-wave propagation law in unfavorable geologic structures with discontinuous deformation analysis method

The propagation of elastic P-wave in unfavorable geologic structures is a complex process which contains reflex, transmission, and refraction. In this paper, the discontinuous deformation analysis (DDA) method is introduced, and the viscous boundary condition and stress wave input way are applied to enable the DDA method to simulate the seismic dynamic response of underground rock mass. The improved DDA program is used to analyze the propagation laws of elastic P-wave in joints and weak interlayer. The results show that (1) for a range of joint stiffness, the difference of transmission coefficient of joint surface between DDA calculation and theoretical solution is small; (2) the lower the joint stiffness, the more obvious the attenuation of the elastic P-wave is; (3) varied joint spacing and joint number play different roles on the attenuation of elastic P-wave; (4) the DDA calculation result is consistent with the theoretical solution for the transmission coefficient of interface; (5) the thickness and elastic modulus of weak interlayer will affect the interference effect of multiple transmission waves; (6) with the increasing weak interlayer thickness H (or a), the attenuation of the elastic P-wave is more obvious; and (7) the lower the wave impedance ratio of weak interlayer, the more obvious the attenuation of the elastic P-wave is.

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

AbstractThe 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 mo...