To explore the strength characteristics of anisotropic rocks caused by mineral directional arrangement during progressive failure process

biotite quartz schist was taken as an example

and triaxial compression tests were carried out on samples with schistosity angles of 0°

45° and 90°. The macro and micro failure characteristics and progressive failure strength index of the specimens were analyzed

and the differences with other types of anisotropic rock were discussed. The results show that the failure characteristics of biotite quartz schist are closely related to its schistosity. With the schistosity angle increasing from 0° to 90°

the main macro and micro fracture modes of the specimens change from tensile to shear

and then to co-existence of tensile and shear. The strength characteristic values of biotite quartz schist show significant anisotropy. With the increase of schistosity angle

the strengthening effect caused by confining pressure increase on the strength characteristic values weakens

but the change of the strength value has a trend of acceleration. The anisotropic variation law of the ratio of strength characteristic value is not obvious

which gradually weakens and even disappears under high confining pressure. The fracture modes

variations of strength characteristic values and their ratios of anisotropic rocks with directional arrangement of minerals are different from those of rocks with stratified structure. A thorough understanding of the mechanical properties of rocks with directional arrangement of minerals will be helpful to guide the related engineering practice.