The "stratum-structure" interaction constitutes a unified load-bearing system, forming the fundamental concept in the design and construction of underground engineering. In the actual operation of tunnels, focusing solely on the structural damage is insufficient; the interaction between "surrounding rock-structure" must be fully considered. Therefore, the damage and failure process of surrounding rock itself are also a key focus of this research direction. The research team has made the following achievements in the study of the disaster-causing process of the "surrounding rock-structure" load-bearing system:
(a) At the component level, for the assembled underground structural sleeve connectors, indoor pull-out tests and finite element simulations were conducted. It revealed that under ultimate load conditions, the damage mainly concentrated on the grout surface of the connectors. The ultimate bearing capacity and the depth of steel reinforcement embedment showed an exponential relationship.
(b) Regarding the damage-causing process of underwater tunnel lining under seismic actions, multi-level finite element detailed simulations were carried out. Considering the interaction between "surrounding rock-structure," the study focused on the crack patterns and component failure mechanisms of the underwater shield tunnel linings under different seismic intensity conditions. It revealed that the damage distribution pattern of shield tunnels under seismic actions is closely related to the direction of seismic waves, mainly located in the bolt fastening segment. Under positive moments, joint opening exhibited a pattern of increase-decrease-increase, significantly different from the case of negative moments. Additionally, increasing the bolt pre-tightening force can reduce crack propagation, but excessive pre-tightening force can lead to bolt breakage. The study suggested that for the specific engineering context, the optimal bolt pre-tightening force should be 360 kN.
Students: Mr Zhuohua Peng (2018 intake, 2021 graduated), Mr Zhenyun Zhao (2021 intake), Mr Hongyi Deng (2022 intake)
Collaborator: Prof Weiyun Chen (Sun Yat-Sen University)