Ground fissures pose serious hazards to underground, as well as aboveground, structures. In underground railways, which are near ground fissures, the potential for disasters is even higher since tunnels face threats from fissure activities. To determine the interaction between a tunnel and ground fissure in the event of an earthquake, field surveys and data analysis were applied to study the activity and damage caused by the fissure. Shaking table tests and a numerical simulation model were used to understand the dynamic response of the fissure site and tunnel. The fissure site had a clear hanging wall effect, where the acceleration amplification was larger in the hanging wall than that in the footwall both on the surface and at the middle of the fissure site. The zone of influence was also wider in the hanging wall. The acceleration magnification factor increased with the burial depth and peak acceleration of the input earthquake. The peak ground acceleration (PGA) decreased with the burial depth on both sides of the fissure. The greatest PGA coefficient was obtained at the surface of the site. The vertical soil pressure was influenced by the metro tunnel and fissure. The vertical soil pressure was larger in the hanging wall, especially in the zone near the fissure, but was less near the tunnel. The horizontal soil pressure above the tunnel was less than that near the fissure. The results of this study are essential for the safe design of underground railway systems.
Shaking table model test and numerical simulation model were conducted on scaled tunnel model to investigate the mechanism and effect of seismic loadings on metro tunnel which is closely parallel to an active ground fissure. Key technical details of the experimental test were set up; for example, similarity relations, boundary conditions, sensors layout, and modelling methods were presented. Synthetic wave, El Centro wave, and Kobe wave were adopted as the input earthquake waves. Results measured from shaking table model and numerical model were compared and analyzed. It is found that the fissure increased the dynamic response features as accelerations and strains of the tunnel, especially in the part close to the fissure. Average incremental percentage of acceleration amplifying coefficient was 8.33% from the wall close to fissure than the symmetrical one. The short distance to fissure led to serious circumferential dynamic strain, while the distance to fissure influenced the axial dynamic strain less. The numerical analysis results have a good correspondence with those of the shaking table model test. The waves at the top of tunnel have more scattering and emission effect. The fissure increases the dynamic response of the tunnel close to it.
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