基于非均质系数的裂隙岩体表征单元体研究

Investigation of the representative elementary volume of fractured rock mass using the homogeneity index

表征单元体(REV)是岩体力学中的一个基础性概念,其存在性是确定岩体等效参数和应用连续介质方法进行研究的前提条件。为综合反映裂隙大小、产状和密度对岩体REV的影响,本文提出采用岩体非均质系数HI来确定岩体的REV。首先,详细介绍了非均质系数的概念和含义。利用General Block软件建立了中等间距-中等延展性(MS1-MP1)裂隙的网络模型,并完成20次随机实现。从各模型中选取10个不同尺寸的岩体模型计算非均质系数,结果表明:非均质系数具有明显的尺寸效应,当岩体尺寸不小于8 m时,非均质系数的平均值和标准差分别为0.5和0.14,综合确定该岩体的REV为8 m。采用HI对三峡地下电站厂房围岩的研究表明,该岩体的REV为60 m,可作为非连续介质方法适用性的判断标准。HI是从岩体结构角度提出的新指标,适用于确定岩体的REV和统计范围,对岩体的统计分析和等效参数研究具有重要意义。

Representative elementary volume(REV)is a fundamental concept in rock mechanics and its existence is a prerequisite for estimating the equivalent parameters of rock mass and applying the continuum method to investigating the rock mass.To comprehensively consider the effects of fracture size,orientation and density on the REV of rock mass,the heterogeneity index(HI)is presented to estimate the REV.The concept and meaning of HI are elaborated and 20 random realizations of fracture network models with moderate spacing and medium persistence are implemented using the General Block software.For each realization,ten rock mass models with different sizes are selected to calculate the HI.The results show an obvious size effect of the homogeneity index.The mean value and standard deviation of the homogeneity index are 0.5 and 0.14,respectively,when the size of the rock mass is not less than 8 m,and the REV for the rock mass is determined to 8 m.The investigation of the surrounding rock mass of the underground powerhouse in the Three Gorges using the HI shows a REV size of 60 m,which can be used as a criterion for the applicability of the discontinuous method.HI is a new index proposed from the perspective of rock mass structure,which is suitable for determining the REV and statistical range of rock masses.It is of great significance for the statistical analysis and investigation of the equivalent parameters of rock masses.