Damage Analysis of Utility Tunnel Crossing Ground Fissure under Dislocation of the Hanging Wall and Footwall

In cities with dense ground fissure distributions, linear infrastructures like underground utility tunnel UUT) inevitably intersect with ground fissures. The vertical displacement between the hanging wall and footwall poses a significant threat to the safety of UUT in ground fissure site. For this reason, taking the UUT in Xi'an Happiness Forest Belt as the prototype structure, 3D finite element models that considered the soil-structure interaction were developed. The strain distribution, damage characteristics of the UUT, and the stress variations in the site soil under different dislocation magnitudes were analyzed. In addition, a damage index was introduced to establish the classification criteria DS0-DS3) for the safety evaluation of the UUT in order to assess the structural damage. The results indicate that: The tensile damage areas in the UUT are concentrated in the upper level compartment of footwall, the wall at the fissure location, and the lower level compartment of hanging wall; the compressive damage areas are concentrated in the wall at the fissure location; the main damage in the UUT is primarily controlled by tensile damage; the weak areas of the UUT are the bottom slab of the lower level large compartment in hanging wall, the side wall of the lower level large compartment at the fissure location, and the top slab of the upper level large compartment in footwall. When the vertical displacement reaches 300 mm, the plastic zone of the upper soil of the hanging wall UUT develops upwards and runs through the soil. Most of the damaged areas of the UUT reach DS3, causing large-scale concrete peeling and structure failure.