The Influence of Bedding Angle on the Tensile Strength and Failure Mode of Bedded Sandstone

To study the influence of different bedding angles to bedded sandstone tensile strength and failure mode, the Brazilian disc split test, which contains 7 types of bedding angle(0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, 90 degrees) , has been conducted. The study results show that: (1) The bedding angle has important effect on bedded sandstone's tensile strength, and the tensile strength of sandstone gradually increases with the increasing of bedding angle(theta) , for which the increasing trend is slow when theta <= 15 degrees and theta >= 75 degrees, and noticeable when 15 degrees <= theta <= 75 degrees. (2) According to the characteristics of relation curve between the bedded sandstone's tensile strength and the bedding angle, the empirical formula of tensile strength and bedding angle has been established, the fitting curve of which can preferably reflect the influence of bedding angle to the bedded sandstone's tensile strength. (3) As the shear strength of the bedding plane is relatively weaker , it is easy to produce shear slip deformation along with the bedding plane under loading effect.This trend of shear sliding has obvious induced effect to the development of fracturing cracks, which in forward causing the fracture surface development of line shape or arc shape. During the process of the bedding angle increases from 0 degrees to 90 degrees, the fracture surface of samples experiences as follows: regular fracture surface -> line or arc fracture surface -> regular fracture surface.