Abstract: Uniaxial compression test was conducted on sandstone with a single pre-existing flaw at various inclined angles. Employing crack propagation measuring techniques and relevant fracture criteria, some conclusions are drawn as follows. (1) The crack initiation angles of the sandstone specimen obtained from both theory and experiments increased with increasing flaw inclined angle. (2) Using a fracture criterion, the appearance of a anti-wing cracks at the tip of the crack of the sandstone specimen was attributed to shear failure. (3) Under uniaxial compression, crack propagation in the sandstone specimen is influenced by the single flaw inclined angle; a small flaw inclined angle it is not easy to crack initiation, while the large flaw inclined angle, allowed easy crack initiation (4) Under uniaxial compression, crack propagation in the sandstone specimen, which was influenced by a single pre-existing flaw, was unstable when the flaw inclined angle was small; and stable when the angle was large. (5) For the sandstone specimen, the average crack propagation velocity for A and B sides of the crack tip decreases with increasing flaw inclined angle.

Key words: flaw inclined angle, anti-wing crack, crack velocity