STRENGTH AND FRACTURE CHARACTERISTICS OF SANDSTONE CONTAINING COPLANAR FISSURE GROUP

The mechanical behavior of joint rock is an important factor in underground engineering stability analysis and support design. By employing rock mechanics servo testing system, a series of uniaxial loading tests were conducted on sandstone samples containing coplanar fissures to investigate the strength and failure characteristics of sandstone with different connection rate and filling pattern. The results show that the mechanical parameters of sandstone containing fissures are remarkably lower than that of intact sandstone. Peak strength, peak strain and elasticity modulus of sandstone samples all decrease gradually with the increase of connection rate. Tension crack I and shear crack II appear successively at the end of preset fissures during sandstone samples failure, and the ultimate failure surface of sandstone samples is formed by crack Ⅱ. The angle between preset fissures and extending cracks (Ⅰ and Ⅱ) increases gradually with the increase of connection rate. Also, the filling pattern has a significant influence on the strength and deformation behavior of sandstone samples, and relatively smaller effect on the modulus elasticity.