Abstract: The fissures have a significant effect on the mechanical properties of rock mass. Based on the experimental results of intact sandstone samples under uniaxial compression, the strength and deformation characteristics of sandstone samples containing z-type fissure are studied by the method of particle flow simulation. At the same time, the effects of inclination angle of ? (the angle of the upper and lower parallel fissure) and ? (the angle of the middle connecting fissure) on the strength, deformation and crack propagation mechanism of sandstone samples containing z-type fissure, and the fracture evolution mechanism of these samples are analyzed. The results show that the elastic phase is significantly shortened; and there are more stress-dropping of sandstone samples containing z-type fissure during the process of deformation. The peak strength and elastic modulus of the rock mass are obviously weaken by the z-type fissure; and the deterioration of the peak strength is greater than the elastic modulus. The peak strength and elastic modulus are increased with increasing of ? and ?, and the influence of ? on the deterioration of mechanical properties is greater than ?. The initial cracks mainly appeared at or near the crack tip; and the initial stress level is between 0.6 and 0.7. The failure modes of the sandstone samples containing z-type fissure can be divided into tensile failure, shear failure and tensile-shear mixed failure; and the main failure model is tensile-shear mixed failure. The stress mutation point on the stress-strain curve corresponds to the jump points of the accumulation curve of microcracks.

Key words: Z-type fissure, fissure angle, strength behavior, crack coalescence, particle flow simulation