EXPERIMENTAL STUDY ON THE FAILURE OF SANDSTONE WITH NOTABLE BEDDING UNDER LOADING AND UNLOADING

The anisotropy rules of stratified rock under loading or unloading are significant to guide the engineering design and construction. The research results on the failure of sandstones with notable horizontal or vertical bedding in Yichang shows that: 1) there is a certain correlation between the rebounding data, longitudinal wave velocity and strength of rock. The basic law is that the larger the rebounding data or longitudinal wave velocity, the higher the strength of the rock. 2) No matter in the failure mode of loading or unloading, the strength of the sandstones with vertical bedding is normally higher than that with horizontal bedding under the same confining pressure. 3) No matter the sandstones with horizontal or vertical bedding, under low confining pressure, the unloading failure peak strength of which is higher than that under loading condition, but under high confining pressure, the phenomenon is opposite. 4) The loading and unloading failure modes of the sandstone are mainly shear failure. The predicted values of failure angle of the sandstone specimens according to Mohr-Coulomb criterion are very close to the measured values. The fracture surface of the sandstone specimens with horizontal or vertical bedding are not affected by the bedding.