风化花岗岩断层带深隧的坍塌机制及其处理方法

Collapse mechanism and treatments of a deep tunnel in the weathered granite fault zone

Abstract: Tunnelling in the fault fracture zone is prone to collapse accidents. The failure characteristics and mechanism of a tunnel collapse in Qinghai were analyzed based on the theory of rock mechanics, discrete element method (DEM), and in-situ test. The results show that the construction disturbance leads to the activation of the granite fracture zone, in which many fissures are constantly eroded and expanded to conduct water, which is the main reason for reducing surrounding rock stability after tunnel excavation. DEM simulates the failure process of the surrounding rock, and the collapse arch is observed. The uneven distribution of the stress field in the whole model is consistent with the tunnel's asymmetric failure phenomenon. Based on the results, treatments such as grouting, enhanced primary support, and advanced pipe roofs were adopted to improve the mechanical properties of fissures and enhance the stability of the surrounding rock. This case provides valuable lessons for similar tunnels.

Keywords: Deep tunnel; Collapse; Granite fault zone; Fissure; Discrete element

Fig.7. Establishment of random fissure group in the DEM.

Fig.8. The simulated process in the DEM.

Fig. 9. The tangential stress concentration phenomenon in the model.

Fig. 19. Variation curves of structural stress: (a) surrounding rock pressure;(b) steel arch stress.

Ziqi Li, Jinxing Lai, Meng Wang, Junling Qiu, Wenbo Zan, Collapse mechanism and treatments of a deep tunnel in the weathered granite fault zone, Tunnelling and Underground Space Technology, Volume 152, 2024, 105891, ISSN 0886-7798

https://doi.org/10.1016/j.tust.2024.105891.