页岩力学各向异性及其变形特征的试验研究

Experimental Study of Mechanics Anisotropy and Deformation Characteristics of Gas Shale

为深入认识含气页岩力学各向异性及其变形特征,选取典型地表露头页岩,沿与页岩原生层理面呈不同夹角方向取芯,进行纵波波速测试、单轴压缩试验、三轴压缩试验,主要研究含气页岩固有的各向异性及其强度、变形、破裂特征。结果表明:页岩是一种脆性层状岩石,其纵波速度、弹性模量、抗压强度随钻芯角度φ不同存在显著的各向异性;页岩原生层理弱面和围压对其变形、破裂形态有很大影响。纵波速度、弹性模量随钻芯角度φ的增加而降低,抗压强度受弱面影响较大,泊松比变化不明显。单轴压缩时,页岩层理弱面对其破裂形态影响很大,弱面开裂与层间剪切破坏共存;三轴压缩时,围压对其破裂形态影响较大,破裂方式以剪切破裂为主。

For deeply understanding the mechanical anisotropy and deformation characteristics of gas shale, the longitudinal wave speed test, uniaxial compression test and triaxial compres- sion test of rock core specimens obtained by drilling typical out- crop gas shale in different angles with shale primary bedding plane were carried out.The inherent anisotropy, strength, deform- ation and fracture characteristics of gas shale were studied.The results showed that as the angle φ of core drilling was different, the longitudinal wave velocity, elastic modulus and compressive strength of shale were obvious anisotropic ; the weak primary bed- ding plane and confining pressure had a great influence on the shale＇s deformation and fracture modes.As increasing of the core drilling angle ~p, the longitudinal wave velocity and elastic modu- lus de6reased, and the compressive strength were influenced by the weak primary bedding plane,while the Poisson^s ratio didn＇t changed significantly.Under uniaxial compression, the weak pri- mary bedding plane had a great influence on fracture mode, in which the weak plane cracking and interlaminar shear fracture coexisted, while under triaxial compression, confining pressure had a greater impact on fracture mode which was mainly shear fracture.