Study On The Effects Of Pre-Reinforcement In Soft And Weak Rock Tunnels

Based on Hefei-Fuzhou High-Speed Railway Tunnel engineering, using the research means of numerical simulation, reinforcing effects of pre-reinforcement measures of large section tunnel in soft ground were systematically studied. The paper can provide theoretical guidance for safety control of large cross section tunnel. This paper mainly completed the following work:1. Focused on the characteristics of soft rock, the paper studied the application condition and goal of pre-reinforcement, and lay the foundation for the research of mechanical reaction and reinforcement effect of different reinforcement measures.2. The reinforcement mechanism of different reinforcing measures are lucubrated, and the corresponding simulation methods are put forward for the different reinforcing measures, and provided convenience for the following theoretical analysis of reinforcement.3. Based on the practical engineering, three kind of pre-reinforcement measures are studied in detail, focusing on the evaluation of reinforcement effect when parameters changed. The evaluation indexes are the maximum roof settlement, the maximum horizontal displacement of working face, the horizontal convergence of tunnel.4. Based on the ADECO concept, three sorts of combing form of pre-reinforcement are put forward:advanced small pipe with working face bolts, pipe roof with working face bolts, and horizontal rotary jet grouting piles with working face bolts. The different reinforcement effects are evaluated when key parameters change. A contrast of the combined form and single pattern are conducted as well to explore the advantage of the combined form.5. Through the comparison of data obtained from in-situ monitoring, the paper discussed the possibility of full face excavation of Baihua Tunnel using the combined reinforcement method.The results in this paper can provide a helpful reference for the theoretical study and practical engineering of safety construction in poor rock condition. To realize the goal of fast construction, the paper put forward three kinds of combined reinforcement method, and through this way the strength of core soil is enhanced significantly, at the same time, the deformation of working face and settlement of tunnel roof decreases obviously, thus guaranteeing the stability of working face.