Abstract: To investigate the effect of bedding on failure mode, elastic modulus and strength of rock with high porosity under different stress conditions, several groups of triaxial tests on specimen with different bedding angles are conducted with pre-hydrostatic compression and axial stress increasing mode. The results show that the anisotropic quartz sandstone showed different characteristics of deformation damage under different stress conditions. With 30 MPa as dividing line of confining pressure, shear failure mode happened in the range of low confining pressure and as the confining pressure increased, fracture surface turned slope to horizontal and is influenced by the bedding. In range of high confining pressure, under the influence of bedding, failure mode could be divided to shear yield and volumetric yield. As the confining pressure increased, the number of newly closed crack reduce, the effect of anisotropy to elastic modulus showed reducing trend and the average increasing rate of Young’s modulus decreased. Young’s modulus of all specimen declined at bedding angle = 60°. Strength curves of different specimen with different bedding angles showed U shape. The minimum compressive strength in range of 0-20 MPa confining pressures showed at the bedding angles = 30°; while in 30-60 MPa transferred to = 45°. Feature coefficient of compressive strength for quartz sandstone with different bedding angles decreases as the confining pressure increases, and keep constant as confining pressure is over 30 MPa.

Key words: rock bedding, triaxial test, anisotropy, failure mode, confining pressure