Earthquake analysis of a venting tunnel considering material nonlinearity and radiation damping of unbounded foundation

Abstract For dams built in seismic active regions, a venting tunnel plays the role in quickly releasing water thus reducing the risk to the dam and downstream area in case of emergency. So the seismic safety of venting tunnels is very important. In the presented research, the earthquake response of a venting tunnel built in an area with strong seismicity is investigated. The venting tunnel including a gate shaft, a framed bent as well as a curved gate chamber is discretized by finite element meshes. The dynamic structure‐water‐foundation interaction is modelled. The water is modelled by added masses, the unbounded foundation is modelled by the visco‐elastic artificial boundary model. Time‐history analysis is performed in the framework of linear‐elastic theory to compute the elastic response of the venting tunnel for excitation of design earthquake. In addition to that, nonlinear time‐history analysis is carried out to investigate the damage of the structure. The nonlinearity of the concrete is simulated by the concrete damage plasticity (CDP) model as proposed by Lee and Fenves and embedded in the commercial software ABAQUS. As shown by the numerical simulation, regions with high stress include mainly those where the flow passageway joins with the front walls, side walls and base slabs, etc. For the nonlinear response of the structure, damage is observed at regions with high tensile stress as indicated by the linear analysis. Reinforcement is suggested to improve the seismic performance of the structures. The proposed research is meaningful for seismic design of venting tunnels in seismic regions.