Abstract:Research purposes: Geological conditions of mountain railway tunnels are complex, the tectonic effect is extremely strong, and the rockburst is frequent, which often cause deformation, cracking and even collapse of the supporting structure, etc. It is of great significance to carry out scientific and reasonable risk assessment and take targeted protective measures. Based on the comprehensive analysis of the large deformation failure characteristics and occurrence law, a complete large deformation evaluation index system is constructed. The weight coefficients of each index were comprehensively determined with the combined analytic hierarchy process (AHP) and information entropy weight method (EWM). Based on the theory and calculation rules of the efficiency coefficient method, a large deformation risk assessment model in long tunnel engineering was proposed and applied to of Yangjiaping Tunnel. Research conclusions: (1) Large deformation is closely related to the maximum principal stress of the surrounding rock cave wall, rock compressive strength, strength-to-stress ratio of surrounding rock, rock elastic modulus, surrounding rock grade, geological structure, and groundwater, and evaluation indexes generally reflect the in-situ stress environment, surrounding rock properties and lithological conditions required for large deformation to occur. (2) Combining the analytic hierarchy process and entropy method, by introducing a distance function, combining subjective weighting and objective weighting to establish a combined weighting rule, this paper solves the problem of the difference between a single objective or subjective weight, and makes the determination of the weight of the large deformation evaluation index more consistent practical and more scientific. (3) The accuracy rate of the evaluation result of the model reaches 90.9%, which verifies the feasibility and accuracy of the model, and it can provide a scientific basis for preventing the occurrence of large tunnel deformation disasters, reducing construction losses and safe operation.
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