基于功效系数法和地应力场反演的深埋长大隧道岩爆预测研究

EFFICIENCY COEFFICIENT METHOD AND GROUND STRESS FIELD INVERSION FOR ROCKBURST PREDICITION IN DEEP AND LONG TUNNEL

岩爆是深埋长大隧道面临的主要地质灾害之一,其“孕育-发生-发展”全过程异常复杂,使其成为地下工程中的世界性难题。准确反映地应力变化规律以及区域内地质构造影响,结合实测资料进行岩爆分级预测,对保障隧道前期勘察设计及后期安全施工具有重要意义。根据隧道工程地质资料,通过COMSOL Multiphysics和Rhino建立三维数值计算模型,反演分析得到整个区域的初始地应力场。在综合分析影响岩爆关键因素的基础上,从“储能性-倾向性-突发性”研究角度,选取岩石单轴抗压强度与围岩洞壁最大主应力比(σc/σmax)、围岩洞壁最大切向应力与岩石单轴抗压强度比(σθ/σc)、岩石强度脆性系数(σc/σt)及岩石弹性能指数(W et)作为评价指标。采用熵权法确定指标权重,运用功效系数法加权计算总功效系数值,构建了一种基于功效系数法和地应力场反演的深埋长大隧道岩爆预测模型,并将其应用于川藏铁路桑珠岭隧道。研究结果表明,该模型具有较高的准确性和可靠性,为类似深埋长大隧道岩爆预测提供了一种新的参考。

Rockburst is one of the main geological disasters during construction in deep and long tunnel.The whole process of‘gestation-occurrence-evolution’is extremely complicated.The prediction of rockburst has become a worldwide difficult problem in underground engineering.It is of great significance to accurately reflect the change law of high ground stress and the influence of geological structure in engineering region,and based on the measured data to predict rockburst classification to ensure the preliminary geological survey and safe construction of tunnels.According to the regional geological data of tunnel,we use the COMSOL Multiphysics and Rhino establish a three-dimensional numerical calculation model.By using the boundary load adjustment method,we inverse the whole area of in-situ stress field.Considering the key factors of rockburst comprehensively,four factors are selected as evaluation indexes.They are the ratio of the uniaxial compressive strength(UCS)of rock to maximum principal stress of the cavern(σc/σmax),the ratio of the maximum tangential stress of the cavern to the UCS of rock(σθ/σc),the ratio of UCS to tensile strength of rock(σc/σt),and the elastic strain energy index(W et).We further use the entropy weight and efficacy coefficient method to determine the weight of indexes and the total efficacy coefficient separately.We construct a rockburst prediction model of deep and long tunnel using the efficiency coefficient method and the ground stress field inversion.The evaluation model is applied to Sangzhuling tunnel and compared with the actual situation to verify the result.The result shows that this method has high accuracy and reliability for rockburst prediction of deep and long tunnel.It provides a new basis for the prediction of rockburst in similar underground engineering.