Experimental study on seismic response of underground tunnel-soil-surface structure interaction system

More and more projects of underground structures undercrossing adjacent surface structures have emerged in recent years. The existence of underground structure influences the propagation of seismic wave, and the inertia effect of the surface structure affects both the seismic response of surrounding site and that of underground structures. Thus, the underground structure and near surface structure can be deem as an interaction system. In this paper, in order to investigate the law of seismic response of underground structure-soil-surface structure interaction system, a shaking table model test was designed and implemented. Based on the experimental results, the law of seismic response of such complex system was analyzed. Note that to overcome the limitation of the bearing capacity of shaking table and eliminate the distortion of soil-structure rigidity ratio, the sawdust soil was chosen to model the surrounding site soil. Test results showed that using sawdust soil as a model soil is feasible. Regarding the law of seismic response of interaction system, it was found that the existence of the tunnel structure has weakened the rigidity of the whole model, and therefore, the seismic response of surrounding soil was amplified. However, it was observed that the existence of the tunnel impeded the propagation of seismic wave to some extent and thus reduced the seismic response of the surface structure, especially for lower and medium floors. The existence of surface structure suppressed the seismic response of soil and underground structures. By comparing the test results under different earthquake excitations, it was shown that the seismic response of the system was affected by the type of seismic wave significantly.