宜宾珙县龙马溪组页岩岩石力学性质研究

STUDY OF MECHANICAL PROPERTIES OF THE LONGMAXI FORMATION SHALE IN GONGXIAN COUNTY,YIBIN

为了研究宜宾珙县地区下志留统龙马溪组页岩的力学性质,采集该地区两处露头页岩岩样,用于单轴抗压和抗拉强度试验研究。结果表明:不管是抗压强度还是抗拉强度,D003系列岩样(最大抗压强度范围:24.81~45.56 MPa;最大抗拉强度范围:0.44~4.67 MPa)基本都高于D002系列岩样(最大抗压强度范围:31.82~87.75 MPa;最大抗拉强度范围:3.49~5.45 MPa)。页岩在单轴受压直至破坏的过程中,层理对页岩的破坏模式和破坏载荷有明显影响:页岩层理越发育,破坏载荷就越小,且页岩破裂方向与岩样自身层理方向基本一致。同时,劈裂试验的裂缝断口方向也与页岩本身的层理方向基本吻合。通过对比分析可知,宜宾珙县地区页岩的抗拉强度和单轴抗压强度均具有一定的各向异性,但总体来说,该地区页岩的抗压强度远大于抗拉强度,这表明宜宾珙县地区下志留统龙马溪组页岩在受载时更容易出现拉伸破坏。研究结果可为该地区进行页岩气钻井、压裂改造的设计提供有益参考。

Shale samples from the lower Silurian Longmaxi Formation in Gongxian County of Yibin were collected for the uniaxial compressive and tensile strength tests so as to study the mechanical properties of the shale.The results show that the compressive strength and tensile strength of the D003 series rock samples(maximum compressive strength range is 24.81-45.56 MPa and the maximum tensile strength range is 0.44-4.67 MPa)is basically higher than that of D002 series rock samples(maximum compressive strength range is 31.82-87.75 MPa and the maximum tensile strength range is 3.49-5.45 MPa).In the process from uniaxial compression to final failure,the bedding has obvious influence on the failure mode and failure load of shale.The more developed the shale bedding,the smaller the failure load,and the fracture direction of the shale is basically consistent with the bedding direction of the rock sample.At the same time,the fracture direction in the splitting test is basically consistent with the bedding direction of shale.Comparative analysis shows that the tensile strength and uniaxial compressive strength of the shale in the area have certain anisotropy,and the compressive strength of the shale is much higher than the tensile strength,and the shale is more prone to tensile failure under the same stress.The study provides a useful reference for the design of shale gas drilling and fracturing in the area.