Experimental study on structural response and failure mode of arched pipeline tunnel with straight walls under reverse fault

Based on an arched pipeline tunnel with straight walls passing through an active fault, the model test was conducted under the action of a reverse fault. The vertical displacement, strain, and internal force distribution of the lining were analysed. Additionally, the failure mechanism of the lining was explored in combination with the crack propagation morphology. The research results indicate that: (1) The vertical displacement of the tunnel arch is distributed in an S-shape along the longitudinal direction, and the influence range increases with the fault displacement. While the fault displacement is 50mm, the core affected area is within the fault, and the general affected area is 0.9 D~3.7 D along the fault displacement surface on the hanging wall side and 0.9 D~2.6 D along the footwall side, where D is the tunnel width. (2) The lining near the fault displacement surface experiences tensile failure, with the peak tensile strain mainly occurring at the foot of the wall. The damage to the inverted arch, foot of the wall, and arch foot of the tunnel lining is more severe compared to other areas. (3) The bending moment and axial force of the lining section located within the fault and on the hanging wall side increase rapidly compared to the ones on the footwall side. Due to the intersection angle between the fault direction and the tunnel axis, the internal forces of the tunnel near the fault displacement surface show an asymmetric distribution. The axial force and bending moment in the 45 ° diagonal direction are relatively large, and the lining undergoes torsional and bending deformation. The stress on the wall foot, inverted arch, and arch shoulder is relatively unfavorable. (4) The arch and wall foot of tunnel lining are longitudinally cracked and damaged, and the area near the fault displacement surface is subjected to shear action, accompanied by oblique shear failure of the arch foot and side walls. The research results can provide reference for anti-breaking structural design of the arched pipeline tunnel with straight walls crossing reverse faults.