基于Jointed Rock模型的不同裂隙形态页岩抗压强度研究

Study on the Compressive Strength of Shale with Different Fracture Morphology Based on Jointed Rock Model

摘要: 作为页岩气储集的主要空间和运移的重要通道，天然裂隙在页岩中以多样的分布特征存在。针对不同层理倾角的无裂隙页岩试件开展了单轴及三轴压缩试验，从而获得层理及基质的剪切强度参数。利用页岩压缩试验数据以及其他学者研究成果，验证了Jointed Rock模型对包含裂隙及层理两类不同弱面岩石数值计算的适用性。在此基础上开展了不同层理倾角下，天然裂隙对页岩强度影响的数值模拟试验，研究发现：(1) 对不同层理倾角的页岩而言，裂隙倾角对其抗压强度的影响规律近似，倾角为0˚，15˚，90˚的裂隙对页岩的抗压强度的影响可忽略，倾角为30˚，45˚，60˚，75˚的裂隙对页岩抗压强度影响较大，且影响程度的大小依次为60˚ > 45˚ > 75˚ > 30˚；(2) 相同裂隙倾角对层理倾角为0˚，90˚页岩抗压强度的削弱程度大致相等，对60˚削弱程度略小于前两者；(3) 数据拟合发现，裂隙对页岩抗压强度的减弱程度和裂隙倾角成2次函数关系，和围压与该围压下无裂隙页岩抗压强度的比率成线性函数关系。

Abstract: As the main reservoir space and important migration channel of the shale gas, the fractures are frequently found in shale with a variety of distribution characteristics. The uniaxial and triaxial compression tests under different inclination angles of the non-fractured shale specimens were conducted, so as to obtain the shear strength parameters of foliation and matrix. Through the compression test data and previous literature data, it has shown that the Jointed Rock model is numerically suitable in calculating the rock which contains crack and foliation. The numerical simulation tests of different foliation dip angles and fracture inclination angle were conducted, it found that (1) for the different foliation angles, the influence of fracture angle on the compressive strength is similar, the influence of fracture inclination angle 0˚, 15˚, 90˚ on the compressive strength of shale can be neglected, the fracture inclination angles 30˚, 45˚, 60˚, 75˚ have great in-fluence on the compressive strength and the degree of influence is 60˚ > 75˚ > 45˚ > 30˚. (2) The weaken degree of same fracture inclination angle on shale foliation dip angle 0˚, 90˚ compressive strength is approximately equal and influences slightly on 60˚. (3) The fracture weakening degree on the compressive strength of the shale is two-times-function relation with the fracture inclination angle, and the linear-function relation with the ratio of the compressive strength of the rock under the same confining pressure.