人工单节理砂岩的三轴试验研究

摘要

采用云石胶黏结岩块的方法制备人工节理面,通过直剪试验获得人工节理面的抗剪强度特性,基于完整和单节理砂岩的常规三轴试验,分析不同倾角(0°,30°,60°,90°)对单节理岩体试样力学响应的影响.结果表明:人工节理面在直剪试验中呈现脆性破坏,其抗剪强度符合M-C准则;不同围压下(2.5,5.0和7.5 MPa)完整砂岩的破坏形态和弹性模量基本相同,峰值强度随围压增大;相同围压下(2.5 MPa)不同倾角单节理岩体的破坏形态、弹性模量、峰值强度均不相同,单节理岩体试样的峰值强度-倾角曲线呈反对号“(√)”形,节理倾角对岩体力学性质的影响明显,其中60°节理岩体试样的强度最低,仅为完整岩石强度的19.7％.推导了过圆柱体试样中心任意斜截面内力的三维计算公式,根据其理论预测所得完整岩石的破裂面角度和60°节理试样的破坏方式均与试验结果相符,其吻合度较传统的二维分析更高.%The bonding interface of two intact rocks bonded by epoxy adhesive is taken as an artificial joint,the shearing strength characteristics of the artificial joint is obtained by direct shearing tests,and the behaviors of intact sandstone specimen and sandstone specimen with the single artificial joint (the angle between the joint plane and the minor principal stress are 0°,30°,60° and 90°,respectively) are analyzed based on the triaxial test results.The results show that the shearing failure mode of the artificial joint shows brittleness damage in the direct shearing tests,and the shear strength meets the Mohr-Coulomb theory.The failure modes and Young's modulus of intact rocks are similar under different confining pressures (2.5,5.0 and 7.5 MPa),and the peak strength increases with the increasing confining pressure.The failure modes,Young's modulus and peak strengths of the sandstone specimen with the single artificial joint of different angles are different under the contact confining pressure of 2.5 MPa,the curve of peak strength and joint inclination angle is in the shape of anti-tick ((√)),and the strength of 60° jointed specimen is only 19.7％ of that of intact rocks,indicating that the angle of the artificial joint significantly affects the characteristics of rock mass.3D calculation formulas for the section internal force through the center of the column specimen are derived.Theoretical analyses of the failure modes of intact rocks and 60° jointed specimen are consistent with the experimental results.The matching degree of theoretical analyses and experimental results is higher than that by the traditional 2D calculation formula.