典型结构面分布型式节理岩体室内直剪试验研究

Effect of two joints distribution on mechanical behavior of jointed rock under shear test

针对节理岩体变形破坏及抗剪强度参数确定问题,开展了5种包含两条节理的典型节理分布型式的节理岩体试样的室内直剪试验研究。试验结果表明节理岩体的破坏主要表现为节理控制的节理与岩桥间渐进搭接破坏;对比分析了试验得到的25条应力应变全过程曲线,提出了应力应变曲线分类方法,包括滑动型、屈服型、剪断型、脆断型、剪断复合型五种类型,揭示了不同类型曲线间的转化规律;对基于Lajtai岩桥破坏理论的强度准则进行试验验证,验证结果表明基于Lajtai岩桥破坏理论的强度准则计算得到抗剪强度偏低与试验结果相对误差较小(小于9%),可用于节理岩体综合抗剪强度计算。

Laboratory direct shear tests were conducted for 5 jointed rocks with typical two-joint distribu⁃tions.This process involved constructing a typical jointed rock system modelling device,optimizing the exper⁃imental test system,and designing an overall testing program to obtain videos of the deformation,failure and propagation process of the jointed rocks.According to the experimental results,the stress-strain curves of the samples with typical joint distributions obtained by direct shear tests were composed of an adjust⁃ment stage,a linear elastic deformation stage,an invisible crack stage,a crack propagation stage,and a re⁃sidual deformation stage.In addition,according to the characteristics of crack propagation stage,the stress-strain curves can be reduced to a sliding type,yielding type,shearing type,fracturing type and shear⁃ing combination type.Note that the type of the stress-strain curve was determined by the joint distribution pattern and the normal stress conditions:as the normal stress increases,the shearing combination type will transform to the shearing type,and the shearing type will transform to the yielding type.The deformation,failure and propagation process of a rock mass with a typical joint distribution was a progressive failure pro⁃cess.The failure of the jointed rock model was mainly lapping failure of the joint and rock-bridge.The spa⁃tial distribution pattern of joints exerted a controlling effect on the failure process and the ultimate failure mode of the samples.Furthermore,after verification testing,the strength criterion from Lajtai’s rock bridge failure theory was verified to produce low shear strength and relatively small relative error.