层状页岩力学特性及其破坏模式研究

采用MTS815型岩石力学试验机进行了页岩层理面不同角度取芯的力学试验，获得了其力学参数及破坏模式特征。试验表明：层理面不同角度试样力学性质存在较大差异性，平行层理面试样其抗压强度最高，与层理面夹角为30°时抗压强度最低，弹性模量随取芯角度的增加逐渐降低。单轴压缩，夹角为0°时破坏模式主要为沿多个平行层理面竖向劈裂，夹角为30°时沿层理弱面剪切破坏，夹角为60°时为大角度剪切破坏并贯穿60°弱层理面，夹角为90°时主要为层状拉张破坏。三轴压缩，夹角为0°时试样有多条破裂面，呈劈裂与剪切破坏共同作用；夹角为30°时，沿层理面剪切破坏；夹角为60°时，呈现剪切破坏，剪切破裂面与水平面夹角在45°~50°之间；夹角为90°时，以剪切破坏为主，有多条平行开裂层面。页岩层理面表现出明显的弱面特征，研究结果为水力压裂施工设计提供了技术参数。

Research on mechanical behaviors and failure modes of layer shale

The mechanical characteristics of shale with different beddings coring were investigated by MTS815 rock mechanical test system. The failure modes，deformation and strength characteristics are obtained. The results indicate that: (1) It shows significantly different properties, when the sample paralleled to bedding plane; it has maximum value of compressive strength and minimum value when the sample has a angle of 30° with bedding plane. The elastic modulus deceases with the increase of the coring angle. (2) Under the condition of uniaxial compression, the angle of 0°, the main failure mode is split failure along the beddings; the angle of 30°, it is shear failure along the weakness plane, the angle of 60°, it is wide-angle shear failure along the weakness plane; the angle of 90°, it is stretch-draw failure. (3) Under the condition of triaxial compression, angle of 0°, it shows several failure surfaces, combined split and shear failure actions; the angle of 30°,it shows shear failure along to the beddings; the angle of 60°, it shows shear failure and the angle of failure surface is 45° to 50°; the angle of 90°, it shows shear failure and it has several parallel failure surfaces. The results can provide an important way for fracture optimization design.