Experimental and numerical studies on the seismic response of adjacent horizontal parallel tunnels

Several studies have investigated the seismic performance of single-tunnel structures. However, few studies have focused on the interactions between adjacent tunnels during earthquakes. The interaction mechanisms and in-fluence ranges between tunnels during earthquakes are not clear. Shaking-table tests and numerical parameter analyses were employed to explore the interaction mechanism between two horizontal parallel tunnels during an earthquake. The main influencing factors were tunnel factors (tunnel net spacing, diameter, and buried depth), ground motion factors (type and amplitude), and site soil types. The calculation and analysis results indicate that the net spacing of the horizontal parallel tunnels is a key factor in determining the interaction of close-distance tunnels. The interaction was most apparent when the net spacing of the tunnels was between one and two times the tunnel diameter, which is the most common net spacing used in practical engineering. In addition, the tunnel diameter, buried depth, ground-motion type, amplitude, and soil type can significantly influence the tunnel response. The results of this study can serve as a reference for the seismic design of adjacent horizontal parallel tunnel structures.