Dynamic Response and Destruction Mechanism of Center Diaphragm Support Wall Under Tunnel Blasting

A center diaphragm support wall is an important part of a tunnel's initial support system. However, it is extremely susceptible to damage and developing cracks under tunnel blasting. In this Ganggou Tunnel of 8-lane dual highway project, field tests were performed within the framework of a blasting project for a highway tunnel to study the dynamic response of center diaphragm support walls, and different failure modes were obtained. The ANSYS/LS-DYNA software was used to simulate a model for center diaphragm support walls. A fluid-solid coupling algorithm was selected to simulate the process of rock blasting and the dynamic response of center diaphragm support walls. Different single period charges and distances were considered. The results indicate that the failure modes can be divided into four types, namely, concrete crack, concrete crush, rebar break, and steel arch distortion. Center diaphragm support walls endure repeated tension and pressure under blasting stress waves, and the impact of rock fragmentation and throw is the primary reason for their failure. Moreover, the center and four sides of center diaphragm support walls are extremely susceptible to damage. Changes in the single period charge and distance affect the scope and degree of failure, resulting in different failure modes. The results of numerical simulation are consistent with those obtained from the field test, and indicate that the optimum blasting distance is larger than 40 cm, while the single period charge should be limited to <7.2 kg. © 2019, Editorial Department of China Journal of Highway and Transport. All right reserved.