三峡水库消落带斜坡岩体劣化过程地质强度指标研究

Geological strength index of the slope rock mass deterioration process of the hydro-fluctuation belt in the Three Gorges Reservoir,China

三峡库区消落带岩体劣化研究多针对室内岩样,难以应用到现场岸坡稳定性分析评价中。本文开展了水库实际运行状态下原位跨孔声波测试和井下电视,获取了不同深度下岩体物理力学参数,改进了GSI系统对岸坡劣化带岩体的描述,拓展了广义Hoek-Brown(H-B)准则在劣化带岩体强度动态评价中的应用,得出主要结论如下:广义H-B准则可以评估、描述原位岸坡岩体强度,结合水位循环消落原位跨孔声波测速,改进并构建了GSI量化取值方法;GSI结合广义H-B准则得到的特征深度强度包线表明,三轴受压应力状态可以提高岩体强度,且可明显抑制岩体劣化;脆-延转换线σ1=4σ3计算的H-B准则适用范围表明GSI系统对岩体劣化评价有宽泛的适用性,且随着GSI下降适用范围下降;通过指数回归构建了考虑劣化过程的GSI(t)、Erm(t)时效曲线,并基于GSI(t)解得不同深度结构面处二、三维强度劣化包线。强度劣化包线显示表层结构面的劣化敏感性高于深层,且表层受劣化影响H-B准则适用范围下降最明显;结合多层面GSI(t)曲线可得三维结构面GSI(t,h)时空函数。这种基于消落带原位跨孔声波的GSI(t)时效函数以及二、三维结构面强度劣化包线分析方法为岸坡岩体劣化评估、稳定性分析和工程治理提供了更加科学合理的新途径。

The study of rock mass deterioration of hydro-fluctuation belt in the Three Gorges Reservoir ar⁃ea is mainly focused on indoor rock samples,which is difficult to be applied to the stability analysis and evaluation of the site bank slope.In this paper,the in-situ cross hole acoustic wave test and downhole TV are carried out under the actual operation of the reservoir,and the physical and mechanical parameters of rock mass at different depths are obtained,the GSI system is improved to describe the rock mass in the deterioration zone of the bank slope,and the application of the generalized Hoek Brown(H-B)criterion in the strength dynamic evaluation of the rock mass in the deterioration zone is extended.The main conclu⁃sions are as follows:The generalized H-B criterion can be used to estimate and describe the strength of in-situ bank slope rock mass.Combined with the in-situ cross hole acoustic velocity measurement of water level circulating drawdown,the GSI quantitative value method is improved and constructed.The strength en⁃velope of the characteristic depth obtained by GSI combined with the generalized H-B criterion shows that the stress state of triaxial compression can improve the strength of rock mass and obviously inhibit the dete⁃rioration of rock mass.The application scope of H-B criterion according to brittle ductile transition line(σ1=4σ3)calculation shows that GSI system has a wide applicability for rock mass deterioration evalua⁃tion,and the application scope declines with the decrease of GSI.The aging curves of GSI(t)and Erm(t)considering the deterioration process are constructed by exponential regression.Based on the GSI(t)solu⁃tion,the two and three-dimensional strength deterioration envelopes at different depth structural planes are obtained.The envelope of strength deterioration shows that the deterioration sensitivity of surface structural plane is higher than that of deep structural plane,and the application scope of H-B criterion decreases most obviously.GSI(t,h)spatiotemporal function of three dimensional structural plane can be obtained by combining the multilayer GSI(t)curve.The GSI(t)aging function based on in-situ cross-hole acoustic wave of the hydro-fluctuation belt and the analyzing method of the two and three dimensional strength dete⁃rioration envelope of structural planes provide a more scientific and reasonable new approach for the evalua⁃tion,stability analysis and engineering treatment of the bank slope rock mass deterioration.