Train Vibration Dynamic Response of Tunnel Invert Under High Geo-Stress

Tunnel arches are susceptible to cracking under high ground stress, which worsens under train vibration loads, posing serious safety risks to train operations. This paper explores the vibration response of tunnel invert with initial crack damage using on-site testing and numerical simulation. Structural cracks often develop at predefined locations within a tunnel structure, particularly at the center of the invert, its outer perimeter, and the invert foot. These regions undergo significant tensile stresses, thus being prone to cracking. The results show that initial cracks cause fluctuation in internal response transmission of the tunnel invert, initially decreasing and then increasing. Response amplification due to structural cracks varies across different positions, with the highest increase observed at the arch foot (25.8%), followed by the center of the inverted arch (24.5%), and the outside of the invert (16.2%). The most critical positions for structural crack damage were ranked as follows: inverted arch foot > inverted arch center > outside of track. By analyzing the relationship between crack size and dynamic response, it is found that the influence of crack width change is greater than that of crack depth change at the same location. This study can provide a fundamental basis for the design of tunnel invert.