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Theoretical Calculation Model for Stability of Tunnel Excavation Face with Pre-grouting Reinforcement
(1. School of Civil Engineering，Southwest Jiaotong University, Chengdu 610031; 2. State Key Laboratory of Intelligent Geotechnics and Tunnelling, Chengdu 610031; 3. Key Laboratory of Transportation Tunnel Engineering，Ministry of Education，Southwest Jiaotong University, Chengdu 610031; 4. Sichuan Vocational and Technical College of Communications, Chengdu 611130; 5. The 3rd Engineering Co, Ltd. of China Railway Construction Bridge Engineering Bureau Group, Shenyang 110043)
Abstract To support the quantitative design of pre-grouting parameters for tunnel excavation faces, a stability cal? culation model for excavation faces considering the effect of pre-grouting reinforcement was established. The ultimate equilibrium method and the strength reduction method were employed to derive a calculation formula for the stability coefficient of the excavation face. The study indicates that the theoretical model's results closely align with numerical models and experimental results, with an average relative error of 4.3%. The stability of the tunnel excavation face is improved with increase in the mechanical parameters of the surrounding rock, cohesion enhancement factor, and the pre-grouting range. The critical grouting range for the excavation face is approximately 0.4D~0.8D;when the pre-grouting range exceeds this critical value, the reinforcement effect is optimal, and the stability of the excavation face is no longer affected by the reinforcement range. A safety coefficient for the excavation face is proposed, considering parameters such as surrounding rock strength, excavation method, unsupported section length,and cohesion enhancement factor, providing a reference for the design of pre-grouting parameters.
Abstract：
To support the quantitative design of pre-grouting parameters for tunnel excavation faces, a stability cal? culation model for excavation faces considering the effect of pre-grouting reinforcement was established. The ultimate equilibrium method and the strength reduction method were employed to derive a calculation formula for the stability coefficient of the excavation face. The study indicates that the theoretical model's results closely align with numerical models and experimental results, with an average relative error of 4.3%. The stability of the tunnel excavation face is improved with increase in the mechanical parameters of the surrounding rock, cohesion enhancement factor, and the pre-grouting range. The critical grouting range for the excavation face is approximately 0.4D~0.8D;when the pre-grouting range exceeds this critical value, the reinforcement effect is optimal, and the stability of the excavation face is no longer affected by the reinforcement range. A safety coefficient for the excavation face is proposed, considering parameters such as surrounding rock strength, excavation method, unsupported section length,and cohesion enhancement factor, providing a reference for the design of pre-grouting parameters.
ZHANG Xiao1,
2 WANG Mingnian1,
2 YU Li1 etc
.Theoretical Calculation Model for Stability of Tunnel Excavation Face with Pre-grouting Reinforcement[J] MODERN TUNNELLING TECHNOLOGY, 2024,V61(5): 42-51
2024, Vol. 61 