Tunnels, Vertical Shafts and Pipelines

Abstract

Traditional belief is that tunnels are not affected much by earthquakes except if an active tectonic fault moves across a tunnel. Dowding and Rozen (1978) studied the response of 71 tunnels in rock to earthquake motions. The damage ranged from cracking to closure in total 42 cases. Sharma and Judd (1991) compiled a database on the response of 192 tunnels during 85 earthquakes throughout the world; 94 of the tunnels suffered from small to heavy damage. More than half the damage reported was caused by events that exceeded magnitude 7 of the Richter scale, and nearly 75% of the damage reported occurred within 50 km of the earthquake epicentre. There was no damage in tunnels where the horizontal peak ground acceleration was up to 0.2g. In most cases where damage was reported, the peak ground accelerations were larger than 0.4g. The data show that shallow tunnels are at greater risk during earthquakes than deeper tunnels; roughly 60% of the total cases had overburden depths less than 50 m and suffered some damage. Ground type is also important; 79% of the openings excavated in soil were reported to have suffered some damage. Dean et al. (2006) reviewed data of 1108 tunnels worldwide with diameters larger than 3 m, of which only twelve were subjected to earthquakes with magnitudes greater than 6 that caused the peak horizontal ground accelerations in excess of 0.16g since 1980. Only four tunnels were reported damaged none of which had precast concrete tunnel linings.