岩石介质弹塑性应变软化本构细观力学参数统计分布模型  

Statistical probability model for mesoscopic mechanical parameters of rock material under elastoplastic strain-softening framework

作　　者：刘建 赵国彦[2] 彭府华 LIU Jian;ZHAO Guoyan;PENG Fuhua(State Key Laboratory of Safety Technology of Metal Mines,Changsha Institute of Mining Research Co.,Ltd.,Changsha 410012,China;School of Resources and Safety Engineering,Central South University,Changsha 410083,China)

机构地区：[1]长沙矿山研究院有限责任公司金属矿山安全技术国家重点实验室,湖南长沙410012 [2]中南大学资源与安全工程学院,湖南长沙410083

出　　处：《煤炭学报》2020年第S02期692-705,共14页Journal of China Coal Society

基　　金：国家重点研发计划资助项目(2016YFC0600702)

摘　　要：岩石的固有非均质性是造成其力学行为复杂性的本质原因。为探究非均质岩石的强度变形及其跨尺度破裂特征,基于连续介质力学理论,分别以正态分布、对数正态分布和Weibull分布描述岩石弹性模量及单轴抗压强度的空间变异特征,以弹塑性应变软化本构模型描述细观单元的力学响应,进而构建一种岩石介质细观物理力学参数统计分布模型。在定义非均匀系数的基础上,首先开展单轴压缩数值模拟,分析3种分布函数下数值试样的应力应变曲线、强度及破坏模式的变化规律;然后开展巴西劈裂数值模拟,探究细观拉压比对均匀试样及非均匀试样起裂点位置及破坏模式的影响。研究结果表明:(1)单轴压缩下,随着均匀程度的降低,数值试样宏观峰值强度与弹性模量逐渐减小,峰值强度对均质度的变化更敏感,应力应变曲线的非线性特征逐渐增强,数值试样依次发生张拉、剪切、塑性流动破坏;(2)压缩荷载作用下非均质岩石内部可产生显著的张拉应力;(3)巴西劈裂条件下,圆盘试样的起裂破坏模式受试样拉压比影响,随细观拉压比增大,试样由中心起裂转变为端部起裂,在满足中心起裂的基础上依据峰值荷载计算出的抗拉强度才是有效的;(4)对于发生端部起裂的圆盘试样,通过峰值载荷计算出的抗拉强度低于试样的真实抗拉强度。The inherent heterogeneity of rocks is an essential reason for the complexity of its mechanical behaviors.In order to explore the strength-deformation characteristics and trans-scale fracture behaviors of rocks,a numerical model based on statistical distribution functions was proposed in the framework of continuum mechanics.The normal distribution,log-normal distribution and Weibull distribution were introduced to describe the spatial variability of elastic modulus and uniaxial compressive strength in each mesoscopic element which exhibits elastoplastic strain-softening mechanical response.Based on the definition of non-uniform indices under different distributions,various numerical uniaxial compressive tests were first carried out to analyze the stress-strain curves,strength and failure modes of specimens with different heterogeneities.Then the numerical Brazilian tests of homogenous and heterogenous specimens were performed respectively to study the effect of mesoscopic tension to compression strength ratio on the positions of crack initiation points and failure modes.The results show that under uniaxial tests,with the decrease of uniformity,the macroscopic peak strength and elastic modulus of numerical samples are gradually reduced,and the peak strength is more sensitive to the change of uniformity,the nonlinear characteristics of stress-strain curves are progressively enhanced.Moreover,the failure modes of numerical specimens change from tensile failure to shear failure and further to plastic flow failure.Significant tensile stress can be produced in heterogeneous rock under compressive loading.With Brazilian tests,the failure mode of numerical disc is affected by the ratio of tensile strength to uniaxial compressive strength of the specimen.As the ratio increases,the initial fracture point will change from the center to the loading points of the disc.Only when the initial fracture point is located at the disc center,the tensile strength calculated from the peak load is effective.For disc samples with crack i

关 键 词：非均质岩石 单轴压缩 巴西劈裂 强度特征 破裂行为 

分 类 号：TU452[建筑科学—岩土工程]