| The surrounding rock of tunnel in soft and crumble area has low strength and its ability to resistance disturbance is poor, to prevent the collapse in excavation process and ensure the tunnel can safely through the soft layers and maintain the stability of the ground surface, the advanced support method is generally used to reinforce the soil ahead of excavation. In our country, pipe roof was first used in the mountain tunnel, and has played an important role in tunnel construction which in shallow area, loose fracture area, joint fault, water gushing and other special geological environment.Based on the Dingjiashan tunnel of Da-Guang highway, according to actual engineering geological conditions, tunnel construction characteristics and environmental conditions, the advance supporting effect of pipe roof was researched. Based on the supporting technology development and application situation of pipe roof in domestic and foreign, the supporting theory was summarized, and combined with the design and construction of pipe roof in Dingjiashan tunnel, according to the characteristics of pipe roof structure, the applicable condition of reinforcement was introduced. According to the current engineering experience and deformation monitoring data of Dingjiashan tunnel, the supporting effect mechanism of pipe roof was concluded, and based on elastic foundation theory, the double parameters model of pipe roof was established to simulate the interaction between pipe roof and surrounding rock. The model is applied in practical engineering to obtain the deflection, angle, bending moment and shear equation of pipe roof by using analytical method, the deformation of steel pipe and internal features in tunnel excavation was analyzed to conclude the influence of selecting of pipe roof on supporting effect.The pipe roof structure of tunnel hole section was simulated by FLAC3D numerical software to analysis the deformation of pipe roof and ground surface settlement under the protection of pipe roof in the tunnel excavation, and to summarize the general rule of displacement of the tunnel hole and ground surface. Meanwhile, the deformation data of the pipe roof and ground surface settlement in tunnel hole section was analyzed to compare with the analytical solution and numerical analysis results, then the design theory of pipe roof in weak surrounding rock was perfect, and the achievements will provide the basis for the selection of parameters for the design and construction.Based on Dingjiashan tunnel project, through the analysis of the tunnel stability under protection of pipe roof in shallow cover and weak surrounding rock, through the elastic theory and the numerical simulation, the deformation of the supporting structure and surrounding rock was predicted to evaluate the effect of pipe roof and to prove that the pipe roof with reasonable excavation way can prevent ground surface settlement and vault sink. It ensures the safety and fast of construction and provides reference value for similar engineering. |
PDF Full Text Request