Abstract:

The control of large deformation of soft rock tunnel with extremely high ground stress is always a difficulty. As a result, field test and data analysis are carried out for core mountain ridge section of Muzhailing Tunnel on LanzhouChongqing Railway. Some conclusions are drawn as follows: 1) The deformation control idea of “release first and then resistance, combination of release and resistance, and anchoring reinforcement” is put forward. 2) The tunnel deformation control scheme of “pilot heading stress releasing+four layers of circular supporting structure+radial grouting+long anchor bolt+long anchor cable” is adopted for the core mountain ridge section. 3) The stress releasing effect of pilot heading is obvious; and the accumulated deformation of main tunnel is decreased about 34%. 4) The deformation law of circular multilayer support structure is obtained. 5) The effect of the large deformation control has been ensured.

Key words: soft rock tunnel with high ground stress, stress releasing of pilot heading, multilayer support, deformation control