Investigation into the collapse height of TBM jamming machinery induced by fault fracture zones and the verification of applicability

Abstract

The large-scale collapse resulting from TBM tunneling within fault fracture zones leads to cutterhead and shield jamming. Given the significant gravitational force of the rock mass and ground stress, the collapse height serves as a key identification factor. Starting with the jamming scenarios of the cutterhead and shield, a mechanical expression for the theoretical model of collapse height is formulated. By incorporating numerical model findings on the extent of rock mass displacement deformation due to excavation disturbance, data from the Xianglushan Tunnel are used to verify the alignment between the theoretical model and simulation results. he findings indicate that the theoretical model-derived collapse height threshold for cutterhead jamming is 7.21 m above the TBM, showing a 90 % agreement with the numerical simulation result of 7.98 m and the maximum collapse cavity height measured in the field (8.0 m). The collapse height of 20.46 m for the shield jamming case corresponds to the open TBM scenario, where shield jamming is less likely. Additionally, the theoretically predicted average collapse heights of 5.31 m, 6.57 m, and 7.51 m under other contact scenarios closely correlate with the simulated displacement deformation zone heights of 5.03 m, 6.92 m, and 7.60 m, demonstrating a 94 % concordance. This theoretical model, showing strong applicability, is further extended to account for varying shield lengths (Ld) and contact range scenarios. For a shield length of 6 m, the predicted threshold value of collapse height for shield jamming aligns with both the theoretical predictions and the simulated rock mass displacement range. This research introduces predictive methodologies for addressing collapse-induced jamming incidents within fault fracture zones.