CHARACTERISTIC OF STRENGTH ANISOTROPY AND FAILURE MODES OF SCHIST

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 α=0°, α=45ånd α=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. FLAC^3D 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 α=90ånd the minimum distribution at α=45°or α=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 α=90°.Otherwise, the maximum value appears at α=0°.