Abstract The exit section (510 m) of the Xiuning tunnel on the rebuilt Chengdu-Kunming railway, passing under the Longtan reservoir, is located in the Luoci-Yimen fault zone. The stratum is composed of rare water-rich mylonite with a classification of grade VI. After excavation, mylonite in the form of plastic flow can easily cause mud gushing and collapse, resulting in large deformation of the primary lining. To pass through this stratum safely and quickly, the deformation of the surrounding rock has to be controlled. Based on a water stability test of mylonite shear strength, this paper presents a support method for this section, namely, full-face pre-grouting with pipe-roof support. Using numerical simulation and deformation monitoring of the surrounding rock and lining structure, it was proven that full-face pre-grouting can effectively achieve water blocking, water squeezing, drainage consolidation and rock strength improvement; pipe-roof pre-support and three-bench seven-step excavation can effectively control rock deformation, ensuring construction safety.
Abstract：
The exit section (510 m) of the Xiuning tunnel on the rebuilt Chengdu-Kunming railway, passing under the Longtan reservoir, is located in the Luoci-Yimen fault zone. The stratum is composed of rare water-rich mylonite with a classification of grade VI. After excavation, mylonite in the form of plastic flow can easily cause mud gushing and collapse, resulting in large deformation of the primary lining. To pass through this stratum safely and quickly, the deformation of the surrounding rock has to be controlled. Based on a water stability test of mylonite shear strength, this paper presents a support method for this section, namely, full-face pre-grouting with pipe-roof support. Using numerical simulation and deformation monitoring of the surrounding rock and lining structure, it was proven that full-face pre-grouting can effectively achieve water blocking, water squeezing, drainage consolidation and rock strength improvement; pipe-roof pre-support and three-bench seven-step excavation can effectively control rock deformation, ensuring construction safety.
SUN Ming-Biao
.Deformation Control for a Large Section Tunnel in Water-Rich Mylonite with Grade Ⅵ
[J] MODERN TUNNELLING TECHNOLOGY, 2014,V51(2): 152-156
2014, Vol. 51 