层状页岩力学特性及其破坏模式研究

Research on mechanical behaviors and failure modes of layer shale

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。

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.