Influence of the water pressure distribution along crack faces on seismic fracture modeling of a dam-reservoir-foundation system

摘要

Hydraulic fracturing of concrete dams subjected to strong earthquakes can be a great hazard, yet the water pressure inside cracks lacks prior investigation. A numerical model based on the polygon scaled boundary finite element method (SBFEM) is proposed to investigate the influence of the water pressure distribution along crack faces on the crack propagation process in a gravity dam during earthquakes. A transient water pressure model that considers the effects of the reservoir head, crack mouth opening displacement, opening/closing velocity of the crack, and relative roughness of the crack faces is utilized. Additionally, contact elements are introduced to avoid possible overlapping of crack faces. The dam-reservoir-foundation dynamic interaction is simulated using a formulation based on the SBFEM, which effectively considers water compressibility, absorption of the reservoir sediments and radiation damping of the unbounded foundation. The numerical results show that the distributions of water pressure along crack faces in the dam under seismic loading are significantly different from those in the static case and can be much higher or lower than the static water pressure, depending on the opening or closing mode of the crack. Further, this difference in turn significantly increases the seismic response of the dam, which leads to longer cracks in the dam.