Failure analysis and dislocation-resistant design parameters of mining tunnel under normal faulting

To investigate the mechanical response and failure characteristic of mining tunnel under the effect of normal fault dislocation and the effect of dislocation resistant design parameters on the tunnel forces, model tests with a geometric similarity ratio of 1:40 were carried out to thoroughly analyze the impact of section connection form and section length on the tunnel. The outcomes of numerical simulations performed at the same scale were then compared to the consequences of experiments. The effect of three anti-dislocation design parameters on the mechanical response and failure characteristic of the tunnel, namely the lining joint form, the lining section length (6 m, 12 m), and the deformation joint width between sections (0.1 m, 0.2 m), was examined on the basis of confirming the accuracy of the numerical model. The results revealed that the tunnel exhibits longitudinal tension-bending superimposed on the vertical extrusion load pattern under the influence of normal fault dislocation, and the longitudinal deformation of the tunnel is characterized by an inverted S-shape. The fault zone is where most of the tunnel devastation is located, and most of the cracks are longitudinal through cracks. The void area appears beneath the invert near the fault plane in the hanging wall, while the loose area appears above the crown near the adjacent fault plane in the footwall. By adopting flexible connections between sections, shortening sections, and increasing the width of deformation joints within a tolerable range, the tunnel can be kept in good operational condition. Due to the difficulties of construction and engineering viability, vertical joints should continue to be the preferred lining form for mining tunnels crossing normal faults. Inclined joints along the fault plane have no evident advantages over vertical joints in terms of internal force.