片岩强度各向异性特征及破坏模式分析

CHARACTERISTIC OF STRENGTH ANISOTROPY AND FAILURE MODES OF SCHIST

为研究片岩的各向异性特征,采用室内三轴压缩试验,获取α=0°、α=45°、α=90°3种片理倾角试样的应力-应变曲线及强度和变形数据。进一步构建7组片理倾角下的标准圆柱体模型,以室内试验获取的数据为依据,反演材料介质力学参数,利用FLAC3D模拟、探讨了不同片理倾角的片岩破坏模式及抗压强度的片理倾角效应和围压效应。结果表明,三轴压缩条件下,片岩的破坏模式主要分为斜切片理剪切破坏和顺片理剪切滑移破坏,对应的变形破坏的控制结构亦不同。相同围压下,片岩抗压强度随片理倾角呈非对称的"U"字型变化,抗压强度最大值始终位于α=90°,最小值分布在α=45°或α=60°处。围压增大时,对顺片理倾角破坏的片岩强度的增强效应趋于弱化。此外,分析了各向异性岩石抗压强度最大值分布位置的影响因素,发现岩石均匀性程度对各向异性岩石的抗压强度最大值的分布有重要影响,均匀性较差时,最大值位于α=90°;反之,最大值出现于α=0°。

This paper examines the anisotropic characteristics of schist. The indoor triaxial compression test is used to obtain the stress-strain curves and the strength and deformation data of schist specimens with three kinds of schistose angles of a = 0°,a = 45° and a = 90°.Then,seven groups of standard cylinder models with different schistose angles are established. The mechanical parameters of model material are selected by back analysis of the laboratory test data. FLAC30 is used to simulate and discusses the failure modes of schist with different schistose angles as well as the schistose angle effect and confining pressure effect influencing compressive strength. The results show that under the condition of triaxial compression, failure modes of schist are mainly divided into shear failure oblique cutting schistose plane and shear sliding failure along schistose plane. The corresponding control structure for deformation and damage is also different. Under the same confining pressure, the compressive strength of schist, changing with schistose inclination,shows the asymmetric “U” type. The maximum compressive strength is always located at a = 90°and the minimum distribution at a = 45°or a = 60°.The enhancement effect of increasing confining pressure on the strength of schist tends to weaken, where the failure mode is the mode of shear-sliding failure along schistose plane. Furthermore, factors impacting on the distribution of maximum compressive strength of anisotropic rock are analyzed by numerical simulation. It is found that uniformity degree of anisotropic rock has important effect on the distribution of the maximum compressive strength. With poor uniformity, the maximum value is located at a = 90°.Otherwise, the maximum value appears at a = 0°.