Shaking table tests on the intersection of cross passage and twin tunnels

The abrupt structural change at the intersection of cross passage and twin tunnels is a potential risk when earthquakes strike. This paper addresses the seismic responses of the cross-passage intersection by shaking table tests. Test data from six cases are presented, where white noise and synthetic earthquake motions are adopted. Discrepant responses between the cross passage and the twin tunnels are described by acceleration data. The extent of discrepancy is quantified statistically. Influence of this discrepancy is evaluated in two directions: dynamic strains of the linings in the transverse direction and circumferential-joint extensions in the longitudinal direction. Since the earthquake-induced dynamic strains are relatively small, they are considered as an insignificant factor. However, there are considerable circumferential-joint extensions near the cross passage. Two simplified models are proposed to estimate the joint extensions in a pseudo-static way. Each model is corresponding to a unique pattern of longitudinal deformation caused by the discrepant responses of the intersection. Test results are compared with analytical results.