Failure analysis and deformation mechanism of segmented utility tunnels crossing ground fissure zones with different intersection angles

Abstract

Ground fissures are a special urban geological disaster within the city of Xi’an. The differential settlement between strata can cause ground cracking and severely threatens the safe construction and operation of underground engineering. This study establishes a 3D-FDM calculation model of different intersection relationships between the segmented utility tunnel and the ground fissures using Flac 3D software. The influence of the intersection angles on the deformation and failure characteristics of the structure was analyzed. The results show that the segmented utility tunnel presents with the deformation characteristic of three-dimensional movement under the action of the ground fissures. The deformation between structures is primarily vertical dislocation, horizontal tension, and compression, indicating that the structure may be subjected to a bending-torsion failure. The vertical settlement of the roof of the utility tunnel shows the deformation characteristics of three broken lines. The third and fourth structures have a significant differential settlement, showing a negative correlation with the intersection angle. The segmented measures can eliminate the void area at the bottom of the hanging wall in the utility tunnel; however, when the intersection angle is ≤30°, the contact pressure at the bottom is close to 0, indicating that the intersection angle has a significant impact on the formation of the void areas. In addition, the calculation method of the vertical settlement of the segmented utility tunnel crossing the ground fissure zone is also proposed. It has proven to be effective in calculating the vertical deformation of the structure. This study provides scientific guidance for constructing utility tunnels within ground fissure development areas.