基于最优赋权-可拓云模型的缓倾围岩隧道底部变形风险综合评价

Comprehensive evaluation of flat rock tunnel bottom deformation risk based on optimal weighting-extension cloud model

针对复杂地质条件下缓倾围岩隧道底部结构变形风险辨识及等级划分不确定性问题,结合缓倾岩层变形机理,建立了包括水文地质、设计施工和施工管理3方面15项影响因素的风险评价指标体系,并将风险等级划分为Ⅰ级(低)、Ⅱ级(中等)、Ⅲ级(较高)、Ⅳ级(高);引入模糊层次递阶结构模型(FISM)和变异系数优化风险因素的主观、客观赋权方法,基于离差平方和(Ward)理论确定最优组合赋权向量。根据云模型数字特征建立可拓云模型,根据最大隶属度原则确定隧道底部变形风险等级。将所建模型应用于川渝山区某隧道工程的3个标段的评价,各标段评价结果分别为Ⅲ级、Ⅱ级偏Ⅲ级、Ⅲ级偏Ⅳ级。结合工程现场变形及FLAC3D模拟结果,验证了缓倾围岩隧道底部变形风险评估模型的可行性。

Aiming at the problem of identification of structural deformation risk and uncertainty classification of the bottom structure of the slowly dipping surrounding rock tunnel under complex geological conditions,this paper combines the deformation mechanism of the gently dipping rock layer to establish a risk evaluation index system of 15 influencing factors including hydrogeology,design construction and construction management,and divides the risk levels into I(low),II(moderate),III(high)and IV(high).The fuzzy hierarchical structure model(FISM)and the subjective and objective weighting methods of optimizing risk factors by coefficient of variation are introduced,and the optimal combination weighting vector is determined based on the sum of squares of dispersion(Ward)theory.According to the digital characteristics of the cloud model,the extendable cloud model is established,and the deformation risk level of the tunnel bottom is determined according to the principle of maximum membership.The established model was applied to the evaluation of three tenders of a tunnel project in Sichuan-Chongqing mountain,and the evaluation results of each tender were III,II,III,III,and IV.Combined with the engineering site deformation and FLAC3D simulation results,which verified the feasibility of the deformation risk assessment model at the bottom of the slowly tilting surrounding rock tunnel.