A comparative study of mountain tunnel subjected to seismic load using 2D and 3D numerical simulations

Abstract: In the 2008 Wenchuan earthquake, more than ten mountain tunnels in operation around the epicenter suffered severe damages. Among all the damaged tunnels, the Longxi tunnel was the most special one which is located at a distance of 2 km from the epicenter of the earthquake. For the seismic design of tunnel structure, an effective simplified approach, two-dimensional finite element model is always built for the certain sections of mountain tunnel to examine the seismic response at the design stage. In the presented study, on purpose of examining the distinction of full three-dimensional numerical analysis and two-dimensional analysis, a full three-dimensional finite element model and four two-dimensional models with different burial depth are built to discuss the seismic response of the Longxi tunnel. The results show that two-dimensional analysis is commonly consistent with the three-dimensional analysis when the burial depth is more than 200m. However, for the shallow buried condition, it is hard to get reasonable result for this simplified approach, and the full three-dimensional numerical analysis is recommended. Furthermore, burial depth has a significant effect on the seismic performance of the tunnel support.