三轴压缩作用下断续节理砂岩力学特性研究

节理岩体的力学特性直接影响工程岩体的安全。为了研究节理岩体的各向异性力学特性和破坏特征,设计进行了0°,30°,45°,60°,75°和90°等6种角度断续节理砂岩的三轴压缩试验,详细分析了节理倾角对断续节理岩体变形强度特征和破坏模式的影响。研究结果表明：①在加载过程中,随着围压增大,断续节理砂岩应力-应变曲线的屈服阶段逐渐明显,峰值强度和残余强度逐渐提高,破坏时延性特征逐渐明显;②随着节理倾角增大,断续节理砂岩的变形模量、抗压强度、黏聚力和内摩擦角等力学参数均呈现先减小后增大的U型变化趋势;③节理对岩样破坏裂纹的形成与开展具有明显的诱导和控制作用,不同倾角岩样的破裂面均顺节理倾角方向发展,当节理倾角与岩样计算破坏角接近的时候,岩样的破裂面顺节理面开展,变形和强度参数达到极小值;④随着围压增大,不同倾角断续节理岩样的变形和强度参数差别逐渐减小,各向异性特征逐渐减弱;⑤断续节理砂岩的破坏模式可分为张拉破坏、折线型的复合剪张破坏、沿节理面剪切破坏等3种类型,节理倾角的分布决定了断续节理砂岩在加载作用下的变形破坏模式,变形破坏模式的差异决定了断续节理砂岩变形和强度参数的各向异性特征。研究成果可为工程中节理岩体的各向异性特征分析提供较好的参考。

Mechanical characteristics of intermittent jointed sandstone under triaxial compression

The mechanical properties of intermittent jointed rock mass directly affect the safety of engineering rock mass. In order to study its anisotropic mechanical properties and failure characteristics, the triaxial compression tests on the intermittent jointed sandstones with 6 joint inclination angles, 0°, 30°, 45°, 60°, 75° and 90°, are performed, and the effects of joint dip angle on the characteristics of deformation strength and failure modes of rock mass are analyzed. The results indicate that: (1) With the increase of confining pressure, the yield phase of stress-strain curve of intermittent jointed sandstone gradually becomes obvious, the peak and residual strengths gradually increase, and the characteristics of ductility are gradually obvious during destruction. (2) With the increase of joint dip, the deformation modulus, compressive strength, cohesion and internal friction angle of rock samples all present U-pattern change. (3) The joints have obvious induction and control effects on the formation and development of rock failure cracks. The fracture surfaces of the rock samples with different joint dip angles develop along the joint dip angle. When the joint dip angle is close to the calculated fracture one of the rock sample, the fracture surface of the rock sample is developed along the joint surface, and the deformation and strength parameters reach the minimum values. (4) With the increase of confining pressure, the difference of deformation and strength parameters of joints with different dip angles gradually decreases, and the anisotropy gradually weakens. (5) The failure modes of the intermittent jointed sandstone can be divided into three types: tensile failure, compound shear failure of fold line, and shear failure of joint surface, and the distribution of joint dip determines the deformation failure mode of sandstone under intermittent loading. The difference in deformation and failure modes determines the anisotropic characteristics of deformation and strength.