Abstract:

The geological conditions of Liangshui tunnel on LanzhouChongqing railway are very complex. The surrounding rocks of the tunnel are phyllite and carbonaceous phyllite, which belong to soft rocks. Serious squeezing deformation and failure induced by high ground stress occur during the construction of the tunnel. In the paper, technologies to control the serious deformation of the soft rocks with high ground stress in Liangshui tunnel is studied on basis of the deformation properties of the tunnel and by means of site testing and theoretical analysis. Conclusions drawn are as follows: 1) The deformation properties and stability of soft rock tunnels (plasticized zone) mainly depend on the ground stress, the mechanical characteristics of surrounding rocks and the dimension of the excavation crosssection, and are closely related to the supporting conditions of the surrounding rocks; 2) The serious deformation of the tunnel has been brought under effective control by adopting such technologies as increasing the deformation allowance, increasing the support rigidity, adopting multiple support, optimizing the construction method and installing the secondary lining timely. Finally, classification standard of serious deformation of soft rock tunnels and corresponding support parameters are proposed.

Key words: LanzhouChongqing railway, Liangshui tunnel, soft rock deformation, high ground stress, deformation control