单轴压缩下龙马溪组页岩各向异性特征研究  

Experimental study on anisotropic properties of Longmaxi formation shale under uniaxial compression

作　　者：侯振坤[1] 杨春和[1,2] 郭印同[2] 张保平[3] 魏元龙[1] 衡帅[2] 王磊[2] 

机构地区：[1]重庆大学煤矿灾害动力学与控制国家重点试验室,重庆400044 [2]中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室,湖北武汉430071 [3]中国石油化工股份有限公司石油工程技术研究院,北京100101

出　　处：《岩土力学》2015年第9期2541-2550,共10页Rock and Soil Mechanics

基　　金：国家自然科学基金资助项目(No.No.51104144);国家重点基础研究发展规划(973)(No.2010CB226701);中石化科技部项目"页岩气水平井分段压裂地应力变化规律研究"(No.P12129);"十二五"国家科技重大专项(No.2011ZX05005-006)

摘　　要：层状页岩的各向异性在页岩气开采中十分重要,以龙马溪层状页岩为研究对象,对不同层理方向取芯、平行于层理面取芯的页岩进行了电镜扫描和单轴压缩试验。结果表明：页岩的微观描述、单轴压缩参数各向异性明显;应力-应变曲线属于Ⅱ类曲线,且5个阶段不明显;破坏类型主要有3种：0°~15°时为竖向劈裂型张拉破坏,30°~60°时为沿层理弱面的剪切滑移破坏,75°~90°时为穿切层理面的剪切破坏,取芯角度不同,对应的曲线之间差异较大。与层理面成30°时单轴抗压强度最小,0°和90°附近相对较大;弹性模量和纵波波速相关性较好,都随着角度的增加而减小;平行于层理面取芯的样品其横观各向异性不明显,可近似看作横观各向同性体;微裂隙发育、独特的破坏类型是造成各向异性的主要原因。The anisotropic behavior of layered shale is particularly important during exploring shale gas. To investigate the anisotropic behavior of layered shale of Longrnaxi Formation in Shizhu County, the scanning electron microscope tests and uniaxial compression tests are conducted on shale specimens cored at different angles to the shale bedding. The results of microscopic features and uniaxial compressive parameters indicate that the shale is distinctly anisotropic. The stress-strain curve belongs to type II and its five phases are not clearly identified. Under the uniaxial compression condition, there are three types of failure mode： vertical splitting tensile damage with the coring angle of 0 ° - 15 ° , shear sliding damage along the beddings with the coring angle of 30 °- 60° ,and shear failure across the beddings with the coring angle of 75 °-90° . Therefore, the curves are significantly different when the coring angles are variable. It is found that the uniaxial compressive strength （UCS） is minimum when the coring angle is 30 ° to the shale bedding; the value of UCS is substantially high when the coring angle is around 0 ° or 90 ° . The elastic modulus is in good agreement with longitudinal wave velocity, and moreover, both of them decrease with the increase of the coring angle. Since it is difficult to identify the transverse anisotropy of cored samples parallel to the bedding plane, the layered shale of Longmaxi Formation is considered as a transverse isotropic body. The micro fracture and the unique destruction type mainly contributes to the anisotropic properties of the layered shale.

关 键 词：层状页岩 层理面 破坏模式 各向异性 力学特性 

分 类 号：TU452[建筑科学—岩土工程]