Seismic damage characteristics and resilience design of cross-fault tunnels: New insights from the Daliang Tunnel in the 2022 Menyuan MW6.6 Earthquake

An earthquake with a magnitude of 6.6 ( M W ) occurred in Menyuan County, Qinghai Province, China, on January 8th, 2022. The Daliang Tunnel, which traverses the seismogenic fault, was severely damaged during this seismic event. The seismic damage investigation of the tunnel is introduced, and the damage characteristics along the tunnel are also presented. It is found that the damage severity of the tunnel is highly correlated with the distance to the fault. Damage modes for different tunnel zones (cross-fault zone, portal zone, and ordinary zone far from the fault and the portal) are quite distinct. Based on the understanding of seismic damage to the Daliang Tunnel in 2022 Menyuan Earthquake, as well as other damaged tunnels during the 2008 Wenchuan Earthquake, the critical influence factors for damage to cross-fault tunnels are discussed. From the seismic investigation, coupling effects of strong ground motions and fault dislocations are highlighted, which pose significant risks to cross-fault tunnels and should be considered in the seismic design for such tunnels. The deformation joints of the tunnel could help the tunnel adapt to the deformation caused by fault dislocation, and thus protect the main structure, but inversely an added local deformation may be expected around the deformation joints. The instability of the overlying slope may have contributed to the local amplification of the fault dislocation along the Daliang Tunnel. Finally, the requirements of seismic resilience for cross-fault tunnels are proposed, and detailed suggestions are provided to enhance the seismic performance of such cross-fault tunnels.