等效晶质模型及岩石力学特征细观研究

AN EQUIVALENT CRYSTAL MODEL FOR MESOSCOPIC BEHAVIOUR OF ROCK

基于颗粒流理论与颗粒流程序,采用颗粒体模型与光滑节理模型,构建具有岩石矿物细观结构特征的等效晶质模型。通过室内试验与计算结果的对比分析,验证等效晶质模型在岩石力学特征研究中的适宜性与可靠性;同时,从细观角度深入揭示岩石在加载条件下的破裂机制与强度特性。主要研究结果如下:(1)在单轴拉伸条件下,岩石近似与加载轴向相垂直的宏观断裂面,主要由相邻晶质体边界上的黏结张拉破坏构成;(2)在单轴压缩或低围压三轴压缩条件下,岩石近似与加载轴向相平行的宏观断裂面,主要以相邻晶质体边界上黏结张拉破坏为主,导致岩石产生宏观劈裂破坏;(3)在高围压三轴压缩条件下,与加载轴向呈一定夹角贯通岩石内部的宏观断裂面,主要以晶质体内张拉破坏以及相邻晶质体边界上黏结张拉、剪切破坏构成,导致岩石产生宏观剪切破坏;(4)对于类似于花岗岩的硬脆性岩石而言,采用等效晶质模型可再现岩石较低的单轴抗拉与单轴抗压强度比值,且其强度特性采用Hoek-Brown强度准则描述更为合理。

Based on the theory of particle flow and the particle flow code(PFC),an equivalent crystal model reflecting the mesoscopic structural features of rock mineral was established with the combination of models of bonded particles and smooth joints. The suitability and reliability of the equivalent crystal model of rock were validated with the experimental and calculated data. The mechanism of fracturing and the strength of rock under loading condition were revealed from mesoscopic viewpoint. Under the uniaxial tensile condition,the surfaces of macro fractures were found to be approximatively perpendicular to the loading direction and the fractures were primarily due to the tensile failure of bond on the boundary of crystalline. Under the uniaxial or triaxial(low confining pressure) compression,the surfaces of macro fractures were parallel to the loading direction and the fractures were primarily due to the tensile failure of bond on the boundary of crystalline,which led to the splitting failure of rock macroscopically. Under the triaxial compression with the high confining pressure,the surfaces of interpenetrating macro fractures cross oblique to the loading direction were primarily due to the tensile failure of bond in the crystalline,and the tensile and shear failure of bond on the boundary of crystalline,which led to the macro shear failure of rock. For hard brittle rock such as granite,the lower ratio between the tensile and uniaxial strength of the rock,can be reproduced by adopting the equivalent crystal model,and its strength properties can be reasonably described with Hoek-Brown strength criterion.