Abstract: The steeply dipped fault zone is the weak link of the seismic stability of underground caverns. Aimed at the complex dynamic interaction characteristics between surrounding rock and faults, based on the Ladanyi’ shear strength model, a seismic deterioration coefficient was introduced, and a shear strength model considering nonlinear mechanical properties and seismic deterioration effect was established. Given the discontinuous deformation characteristics between surrounding rock and faults, a three-dimensional dynamic contact force method was proposed, which considered both the complex shear strength and multiple contact states. The method was applied to Jinchuan underground powerhouse to study its seismic damage characteristics under the influence of the steeply dipped fault F31. The results indicate that after considering the interfaces and seismic deterioration effect, the seismic response of the cavern increases, the dislocation between the surrounding rock and faults is more evident, and a certain depth of separation and sliding failure zones occurs. The steeply dipped fault cuts the high sidewalls of the main powerhouse, and forms a weak zone where the surrounding rock thinness is thin, resulting in larger deformation and damage. The flexural toppling deformation and slipping deformation into the cavern tend to occur on the upstream and downstream sidewalls, respectively. The distribution of the sliding and separation failure zone of the interfaces between surrounding rock and faults changes dynamically with the seismic process and extends to the depth. Among them, the separation zone is relatively large at the arch abutment and rock anchoring beam. The numerical results reveal the dynamic failure mechanism of surrounding rock of underground cavern intersected by a steeply dipped fault, which can provide reference for seismic design.

Key words: underground cavern, steeply dipped fault, dynamic contact method, seismic response, damage characteristics