Analysis of invert heaving considering strength degradation of surrounding rock
Gao Zhen1 Ma Weibin2 Wu Xu1 Wang Sukang1
1. Key Laboratory of Urban Underground Engineering of the Ministry of Education, Beijing Jiaotong University,
Beijing 100044, China;2. China Academy of Railway Sciences Corporation Limited, Beijing 100081, China
Abstract：Aiming at the problem of uplift deformation of the bottom structure of high-speed railway tunnels, based on the theory of strength degradation, this paper gives a model of the uplift deformation mechanism of the bottom structure caused by the decrease of the surrounding rock strength under the condition of muddy sedimentary rock formation. Applying the strength deterioration theory to numerical simulation calculations, the results show that the amount of uplift deformation of the tunnel bottom structure increases with the decrease of the cohesive force of the surrounding rock. The difference between the simulated value and the on-site monitoring data is about 16.1% of the maximum value of the center line, and the difference of the maximum value of the side line is about 11.3%. The deformation tendency of the arch uplift is roughly consistent. Comparing the field measured uplift deformation with the simulated value, it is concluded that the cohesion of surrounding rock decreases with time and becomes non-linear and tends to stabilize, which verifies the applicability of the strength degradation model; As the cohesive force decreases, the plastic zone of the invert arch fill layer gradually starts from the drainage ditch and expands to both sides. When the cohesive force decreases by 40%, the tensile zone of the plastic zone is roughly the same as the crack location on the site monitoring. The results provide a reference for the strength degradation of surrounding rock that should be considered in the future section design of such tunnel structures.
