Abstract
The Juji Tunnel of the Lida Expressway traverses complex and variable highly weathered, thin-bedded shale strata. The surrounding rock is inherently weak and fractured, with severe large deformation occurring after tunnel excavation. The overall stability of the surrounding rock is poor, and under the influence of factors such as great burial depth, extensive loosening zone, and strong strain energy accumulation within the strata, the initial support exhibits high deformation potential. To ensure construction safety, deformation of soft rock in adverse geological conditions is controlled through measures including improving the load-bearing performance and stiffness of the support structure, providing rational deformation allowance, advanced pre-support and multi-layer support, short-bench mechanical rapid excavation method, controlled blasting, and controlled cycle advance. The adoption of advanced support effectively controlled surrounding rock deformation in soft rock sections, increased the construction safety factor, effectively guaranteed project quality, and provided technical support and reference for similar tunnels.
Full Text
Preamble
Research on Large Deformation Control Technology for Tunnel Passage through Complex and Variable Soft Rock
YIN Yongjin (China Railway 16th Bureau Group Fourth Engineering Co., Ltd., Beijing 101400, China)
Abstract
The Juji Tunnel of the Lin-Da Expressway traverses complex and variable highly weathered, thin-layered shale formations. The surrounding rock mass is inherently weak and highly fractured, resulting in severe large deformation following excavation. The overall stability of the rock mass is poor, and influenced by factors such as substantial burial depth, extensive loosening zones, and significant accumulated strain energy within the strata, the initial support system demonstrates considerable deformation potential.
To ensure construction safety, comprehensive measures were adopted to control deformation in these adverse geological conditions. These measures included enhancing the structural performance and stiffness of the support system, providing appropriate deformation allowances, implementing advanced pre-support and multi-layer support techniques, employing short-bench mechanical rapid excavation combined with controlled blasting, and regulating the cyclic advance length. The application of advanced support effectively controlled surrounding rock deformation in soft rock sections, significantly improved the construction safety coefficient, and guaranteed project quality. This methodology offers valuable technical support and reference for similar tunnel engineering projects.
Keywords: Complex and variable; Weak; Poor stability; Initial support; Surrounding rock deformation