山岭隧道大变形危险性评价的功效系数法研究

Efficiency Coefficient Method for Large Deformation Risk Assessment of Mountain Tunnel

研究目的:山区铁路隧道地质条件复杂,构造作用强烈,软弱围岩大变形灾害频发,经常会引起支护结构变形、开裂甚至坍塌等,对其进行科学合理的危险性评价并采取针对性的防护措施具有十分重要的意义。本文通过综合分析大变形破坏特征及发生规律,构建完善的大变形评价指标体系。采用层次分析法和熵权法相结合综合确定各个指标的权重,基于功效系数法理论及计算规则,构建一种隧道大变形危险性评价模型,将其应用于成兰铁路杨家坪隧道大变形危险性评价。研究结论:(1)大变形与围岩洞壁最大主应力、岩石抗压强度、围岩强度应力比、岩石弹性模量、围岩级别、地质构造、地下水密切相关,评价指标总体反映了大变形发生所需的地应力环境、围岩性质和岩性条件;(2)结合层次分析法和熵权法,通过引入距离函数,综合主观赋权和客观赋权建立组合赋权规则,解决了单一客观或主观权重的差异性和片面性问题,使得大变形评价指标权重的确定更加符合实际、更具科学性;(3)本文模型评价结果的准确率达到90.9%,验证了模型的可行性和准确性,可为预防隧道大变形灾害发生、降低施工损失及安全运营提供科学依据。

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.