Numerical study of plastic response of urban underground rock tunnel subjected to earthquake

Abstract

Underground facilities play an important role in infrastructure of modern society, especially some lifeline engineering, such as subway and railway tunnels, civil air-defense engineering and so on. As we know, the entire cognitive processes of seismic response of underground openings to earthquake is transforming from taking no account of earthquake load, primordially, to adopting the theory of free-field deformation, transitively, and the employing theory of dynamic design till now. However, so far, there are no established methods which can absolutely be employed for assessing and evaluating stability and induced plastic damage of tunnel surroundings ground during earthquakes. Based on a while building subway tunnel, this paper describes the propagation of seismic wave and seismic induced plastic damage of surrounding rock with a simple harmonic wave and a field recorded wave, which have the same dominate frequency. In addition, the specific energy density (SED) is introduced to represent the energy dissipation during ground shaking. Due to the recorded time-history wave, the response of feature points along tunnel and extension of plastic zone are analyzed with the different peak ground acceleration (PGA). Results illustrate that the upper tunnel cross section is more vulnerable than the lower part. Interestingly, when the PGA reaches 0.3 and 0.4 time of gravity acceleration, the seismic response of tunnel behaves almost the same.