Mechanical properties of segmented utility tunnels with ground fissure dislocation

Abstract

Abstract Underground utility tunnels provide essential services to the urban population and solve the problem of the shortage of overground space. Although segmented utility tunnels suffer less force and bending moment, their response due to soil movement is more complex, especially when the tunnel crosses the ground fissure zone. This paper investigates segmented utility tunnels' deformation and stress response under different ground fissure dislocations through 3D finite element (FE) simulation. A segmented utility tunnel in Xingfu Forest Belt in Xi’an city, China, is employed as the research object. The simulation results show that, under the orthogonal condition (the utility tunnel orthogonally crosses the ground fissure), the main deformation area of the tunnel was within the range of 30-80m along the longitudinal direction (about 30m away from the ground fissure in the hanging wall and 20m in the footwall). The tunnel showed bending and shear characteristics. The main compression area of the tunnel was mainly concentrated within the hanging wall near the ground fissure, and the stress in the other area was low and generally not changed. Under the oblique condition (the utility tunnel obliquely crosses the ground fissure with an angle of 60°), the main deformation area of the tunnel was within the range of 45-80m along the longitudinal direction (about 15m away from the ground fissure in the hanging wall and 20m in the footwall), and the tunnel showed combined bending-shearing-torsion characteristics. The stress at the tunnel junction changed sharply when crossing the ground fissure. Concurrently, the left warehouse of the tunnel, which was larger than the right warehouse subjected to greater vertical stress. This study provides some reference for the structural design of the segmented utility tunnels when it crosses the ground fissures.