Seismic response of metro tunnel oriented parallel to ground fissures

Under the different magnitudes' synthetic earthquake waves, the acceleration, displacement and internal force were studied by the numerical simulation method for the metro tunnel oriented parallel to ground fissures in short distance, and the influence area of the ground fissures, dynamic earth pressure variation law of the surrounding rock and contacting dynamicearth pressure variation law between the tunnel and surrounding rock were calculated. Analysis result shows that there is an additional magnification area of the acceleration response within a horizontal distance of 25-50 mfrom the ground surface to the tunnel. When the magnitude of the synthetic earthquake wave is smaller (the 50-year exceedance probability is 63%), the relatively horizontal displacements at the top and bottom of the tunnel are smaller (about 0.39 mm), but increase with the increasing earthquake magnitude. The largest displacement is 1.53 mm when the 50-year exceedance probability is 2%. Under the earthquake, the axial forces at the right and left shoulders and foot are larger, and the largest force is 1 926 kN at the right arch foot. The moments and shear forces are larger at the right and left arch waists, and the largest moment and shear force are at the right arch waist and 78.54 kN·m and 1 830 kN, respectively. The internal force increases with the increasing earthquake magnitude. The dynamic earth pressure near the fissure is large and gradually decreases to both sides. Under the earthquake, at the top of the tunnel, the influenced widths of the hanging wall and foot wall are 25 and 20 m, respectively. At the bottom of the tunnel, the influenced widths of the hanging wall and foot wall are 26 and 22 m, respectively. The influence widths of the hanging wall and foot wall of ground fissure increase by about 35% under the large earthquake compared with the moderate earthquake. The dynamic earth pressure variation laws at the top and bottom of the tunnel are similar with and without the fissures, the pressures close to the tunnel are larger, and the largest pressure is 138 kPa. The contacting dynamic earth pressure increment is larger at the arch waist of the tunnel under the earthquake, the maximum increment is 45.27% at the right arch waist (close to the ground fissure), the second increment is 13.41% at the top, and the minimum increment is 6.86% at the bottom.