Investigation of dynamic response of square dual-chamber and bending utility tunnels under gas explosion loads

The gas pipeline is considered as the most potentially hazardous component in the urban utility tunnel. In current work, a numerical model, developed in LS-DYNA, utilizing Arbitrary Lagrangian-Eulerian (ALE) algorithm, accounts for both fluid characteristics of explosion gases and mechanical behavior of structures. Through the analyses of shock wave pressure, structural displacement and effective stress in the square dual-chamber utility tunnel, it is determined that the most vulnerable damage zones under gas explosion loads are located at the inner corners and outer walls of the gas chamber, and their peak effective stresses are 4.875 MPa and 4.363 MPa, respectively. The peak pressure decreases from 0.314 MPa at 6 m from the ignition source to 0.215 MPa at 30 m, with a decreasing ratio of 31.53%. The response of bending utility tunnels with varied bending angles subjected to gas explosion loads are thoroughly examined. Compared with the baseline pressure of straight section of tunnel (0.255 MPa), the pressure gradually increases with the bending angle. The pressure reaches 0.301 MPa for 90° bend, with an increasing ratio of 18%. The displacement is 8.86 mm for the straight section, but it increases to 10.36 mm for the 90° bend. At smaller bending angles of 15° and 30°, the damage area is distributed more evenly, and the overall damage level is relatively slight. However, at larger bending angles of 45°, 60° and 90°, the damages are mainly concentrated in the front and at the bends.