Hydraulic fracture of concrete-rock interface in reservoir-gravity dam-foundation system under seismic conditions

Abstract

Under strong seismic excitation, hydraulic fractures considering ultrahigh reservoir load at the gravity dam-foundation interface adversely affect the stability of the generalized structure. Based on the reservoir-dam-foundation interaction model, dynamic water pressure model, and contact element, a new numerical model that simulates interfacial hydraulic fracture is established by introducing generalized stress intensity factors and the Hutchinson-Suo propagation criterion. Using a preset crack at the dam heel and tracking its trajectory, this study compares the structural damage and crack propagation process in the interface and homogeneity models, investigates the influence of different water pressure distributions along the crack faces on the seismic response of the structure and fracture characteristics, and finally conducts a sensitivity analysis of the parameters in the dam-foundation system. The numerical results show that the presence of the interface between the dam and foundation significantly alters the damage characteristics of the structure and the propagation path of the cracks. Regarding seismic analysis in actual engineering, it is reasonable to assume that the water pressure is uniformly distributed along the crack faces initiated from the dam heel. When the fracture toughness of the foundation rock is less than or greater than that of concrete by up to 14.3%, and the difference is not more than 0.5 MPa·m1/2, the cracks kink into the foundation; otherwise, the cracks may kink into the dam body.