Study on the characteristics and mechanism of seismic damage for tunnel structures on fault rupture zone in Wenchuan seismic disastrous area

Based on the damage reports of highway tunnels in Wenchuan earthquake, statistical analysis is conducted and the main reasons of tunnel structure damage in fault rupture zone are determined as fault dislocation, weakness of surrounding rock and width of fault rupture zone. The damage characteristic of tunnel structures in earthquake are that serious damage, such as secondary lining collapse and tunnel collapse, can be found when fault dislocates, but it will not emerge when fault is stable. Based on the numerical simulation and in-situ damage analysis results, it can be concluded that when fault is wide and it dislocates, tunnel structure damage in fault rupture zone is the most serious wide dislocating area. Both secondary lining collapse and tunnel collapse will emerge, so the precaution should be taken in priority. When fault is narrow and dislocates, tunnel structure damage in fault rupture zone is also critical. When fault is wide and stable, no serious damage like the collapse of the secondary lining will emerge. When fault dislocates, both cross sectional precaution and longitudinal precaution should be taken in tunnel engineering, especially the longitudinal one. When fault is stable, only cross sectional precaution should be taken. The research results can provide reference for anti-seismic precaution of tunnel across fault rupture zone.