【摘要】 为克服物理模拟试验制作大量小尺寸断续节理的困难,采用PFC2D软件对节理连通率固定而节理尺寸(或节理分段数m)与倾角β组合变化的断续节理岩体开展了单轴压缩数值模拟试验,分析了其宏观非线性力学响应和细观损伤力学机理。PFC模型的细观力学参数根据以往的多批含节理石膏试件物理模拟试验结果进行标定。研究发现:(1)当节理倾角固定时,试件当量化峰值强度和弹性模量随节理尺寸(或m)的减小而增大,且峰值强度与Oda组构张量的标量损伤变量呈指数关系。(2)随着节理倾角或节理分段数的减小,试件的应力应变曲线由单峰型变为多峰型,节理系统的承载力调用提升。(3)试件的破坏模式可分为岩石基质剪切破坏、沿同列节理的条块状破坏和沿节理面的剪切滑移破坏3种类型,与后两种破坏模式相比,第一种破坏模式的试件强度较高。(4)节理试件的非线性力学响应与节理和岩桥的相互作用密切相关,并经历了如下3个阶段:弹性变形阶段,节理系统未闭合,岩桥单独承载;非弹性变形阶段,岩桥或基质出现损伤,节理系统开始闭合并承载;残余阶段,由于岩桥或基质破坏以及节理的再次张开,岩桥或基质以及节理系统的承载力都降低。(5)节理和岩桥的非线性力学响应决定了试件的弹性模量、强度、延性随节理尺寸的变化规律;一般而言,随节理尺寸(或m)减小,节理的闭合位移与承载力调用也减少。更多还原

【Abstract】 To avoid the difficulty in fabricating a large number of small joints in physical models of a rock mass,PFC2D modeling was used to investigate the combined influence of joint size(or the number of joint segments m) and joint inclination angle β on the nonlinear macroscopic behavior of the jointed rock mass at constant joint continuity factor under uniaxial compression,and the corresponding microscopic damage mechanism was studied. The microscopic mechanical parameters used in the PFC numerical model were calibrated through previous several laboratory tests on jointed gypsum samples. It was found that:(1) When joint inclination angle is fixed,the unified peak strength and elastic modulus of the specimen increase with the decrease of joint size(or m),and the peak strength is exponentially related to the scalar damage variable of Oda constitutive tensor.(2) When the inclination angle or number of joint segments decreases,the stress-strain curve of the specimen changes from single peak to multi-peaks,and the bearing capacity mobilization of the joint system is increased.(3) Three failure modes have been observed:shear failure of rock matrix,broken failure along the same row of joints,and shear failure along the joint surface. Specimens with the first failure modehave higher strength than those with the latter two failure modes.(4) The nonlinear mechanical response of the jointed specimens can be attributed to the interaction between the rock bridges(or rock matrix)and the joints,which can be divided into the following three stages:elastic deformation stage,in which the joint system is not closed and the rock bridge bears the load alone;the nonelastic deformation stage,in which damage occurs in the rock bridges or matrix while the joint system begin to close and their bearing capacity is mobilized;the residual deformation stage,either the loading capacity of the rock bridges or matrix or that of the joint system decreases due to the failure ofthe rock bridges or matrixand and opening again of the joint system.(5) The nonlinear mechanical response of the joints and rock bridges determines the variation of elastic modulus,strength and ductility of specimens with joint size. In general,as the joint size(or m) decreases,the closure displacement and bearing capacity mobilization of the joint system decrease.更多还原