TBM jamming analysis and efficient release technology in water-rich fault fracture zone

Abstract

Due to the rock mass' s poor stability in the water-rich fault fracture zone, the large-scale and difficult-to-handle TBM machine jamming disasters often happen when TBMs pass through such regions. The jamming incident of an open TBM in a water conveyance tunnel located in Xinjiang was taken as an example to analyze the causes of local large deformation of the supporting structure and the convergence deformation characteristics of the tunnel surrounding rock near the main fault surface. Based on the analysis of on-site engineering geological conditions and structural deformation, it was determined that the jamming incident was caused by the rupture, expansion and deformation of the left and upper surrounding rocks under the influence of excavation disturbance, which exerted a large squeezing effect on the shield, causing the mutual friction between the surrounding rock and the shield greater than the TBM's maximum thrust. Through numerical simulation analysis, the fractured surrounding rock on the upper left side showed an overall mechanical response of sliding along the main slip surface of the fault besides volume expansion and deformation. Therefore, under the effect of water flow, the initial shield and steel arch were severely damaged. In addition, the simulation result show that as the jamming time increases, the scope and severity of the jamming will intensify. Specifically, the surrounding rock of the vault also gradually undergoes obvious expansion and deformation, causing the shield to be affected by the circumferential force within the scope of 270°. Based on the classic elastic foundation beam theory, the easily deformable range of the supporting steel arch was calculated, further explaining the severe deformation phenomenon of the steel arch and shield in this jamming case. Finally, according to the on-site construction conditions, domestic and foreign engineering experience, and the above-mentioned analysis of the jamming disaster breeding process, an efficient TBM release theory of "tight-injection-excavation" is proposed. After the dense steel arch and chemical grouting were implemented, a strong pressure-bearing arch effect was formed around the tunnel. With the subsequent excavation release technology, the TBM was successfully continuing operation.

Keywords

local deformation / swelling deformation / elastic foundation beam theory / TBM escape