Abstract: The existence of the joints is an important characteristic of rock mass distinctly different from rock, and also an important factor leading to the heterogeneousness and anisotropy of rock mass.On the basis of the analysis of the mechanism of blast failure mode of rock mass affected by joints, a new numerical method, or numerical manifold method, which can perfectly simulate the joint distribution in rock mass and the occurrence and propagation of cracks, is adopted to simulate the failure process of three rock masses with such joints as no joints, averagely distributed horizontal joints or averagely distributed vertical joints respectively under the blast impact load perpendicular to the circumference.From the simulation results, it can be evidently seen that the existence of the joints plays a vital role in controlling the failure form of rock mass.The failure form of the intact rock mass has good symmetry, while for rock masses with horizontal joints or vertical joints, their failure forms are controlled by the distribution of the joints to large extent.

Key words: Jointed rock mass, Blast failure, Failure mode, Mechanism analysis, Numerical manifold method