The values of geological strength index (GSI) are always regional and have an influence on the application of Hoek-Brown criterion.In this article,back analysis was performed for geological strength index (GSI),disturbance factor D and Poisson ratio based on the Hoek-Brown criterion for the tunnel from Yongping Road to the North Station of Qingdao Metro Line 3.Uniform design table was employed to deal with the range of parameters and the selection of experimental points for back analysis to reduce the number of experiments and guarantee better experiment results.Furthermore,the GSI values of 10 different cross-sections were calculated by FLAC3D software and the relationship between GSI and rock mass ultrasonic velocity (Vp) was obtained using linear fitting method.The formula of GSI-Vp was applied to estimate the GSI values for the tunnel from Middle Chongqing Road to Yongping Road of Qingdao Metro Line 3.The calculated result was in good agreement with monitoring data,which verifies the rationality of the GSI-Vp formula and provides a new approach for accurately obtaining the GSI values.%地质强度指标GSI的选取有地域性,GSI的准确性会直接影响Hoek-Brown强度准则的应用效果.基于Hoek-Brown准则对青岛地铁3号线永平路站—青岛火车北站区间内的地质强度指标GSI、扰动系数D和泊松比进行反演研究,并利用均匀设计表对反演参数进行范围划分和试验点选取,有效降低了试验次数,同时保证了较好的试验效果.借助FLAG3D软件计算出10个断面的GSI值,并研究了GSI与岩体波速Vp的关系,通过线性拟合得到GSI-Vp关系式,并用于预测青岛地铁3号线重永区间的GSI值.结果表明:GSI-Vp关系式所预测的GSI值用于重永区间数值模拟计算,所得位移值与该区间监测值的相对误差较小,具有较好的一致性,进而验证了关系式的合理性.研究成果为工程上准确获得GSI提供了新方法.
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