Seismic damage of mountain tunnels during the 5.12 Wenchuan earthquake

A number of mountain tunnels suffered significant damage to various extent during the 2008 Wenchuan earthquake in China. Damage ranging from small to heavy cracking was observed both at the portal and inside the tunnels, while some sections close to the faults completely collapsed. A summary of qualitative data collected from reports and papers is presented regarding the behavior of the 55 mountain tunnels near the epicenter during the earthquake. Based on the seismic investigation and data collection of mountain tunnels, the tunnel damage is classified into six most common damage models involving cracking, spalling, shear failure, dislocation, pavement uplift and collapse. Detailed study and discussion are then carried out on the damage models. In order to examine the influencing factors of the damage magnitude of the mountain tunnels, the correlations between epicentral distance, earthquake intensity, overburden depth, geological condition and damage levels are analyzed. The relationships between earthquake parameters and different damage models are developed and discussed. Also, suggestions are provided to improve the seismic resistance of mountain tunnels.