Research on Damage Modes of Shield Tunnel under Near-field Explosion Load

In order to study the damage mechanism of shield tunnel under near-field explosion load, the explosion condition of 23 kg TNT with the center distance of 300 mm was selected, and the near-field explosion condition of five locations such as vault, spinner, arch, arch foot and arch bottom was analyzed by finite element method, and the damage distribution law of shield tunnel was summarized. Through LS-DYNA finite element analysis, it is found that under the action of near-field explosion, there is significant damage to the shield tunnel segments, among which the inner side damage is the most significant, with the minimum area of 54 dm², followed by the section and back of the segment with the minimum damage area of 38 dm² and 32 dm² respectively. When the explosion point is located at the spandrel and arch foot, the damage area is the largest. Because the explosion point is close to the joint of the ring joint and the longitudinal joint of the segment, the intensity of this area is relatively low, and the reflection of the shock wave increases. When the joints (annular joints and longitudinal joints) are subjected to near-field explosion load, the damage distribution is symmetrical and circular. However, when the joint intersection is subjected to near-field explosion load, the damage increases significantly and is unevenly distributed.