Abstract: The removability and stability analysis of rock block are carried out independently in the classical block theory which tacitly approves the nonremovable block being absolutely stable and thus skips the stability analysis. However, in the practical engineering project, the “rock bridge” preventing the movement of rock block may crack, resulting the sliding of the nonremovable blocks. The likelihood of the cracking under gravity would increase with the size of block. This paper proposes a stability analysis method considering the cracking of the rock bridge. The nonremovable blocks are no longer assumed to be absolutely stable. When calculating the block stability factor, this method integrates the shear resistance of the rock bridges into the anti-sliding force of the block. Firstly every possible sliding surface and the intersection line of fractures are listed. Then the rock bridges damaged along each possible moving direction are determined. Afterward, the stability factor along each direction is calculated based on the Mohr-Coulomb yield criterion. The minimum stability factor is selected as the actual stability factor of the block and the associated moving direction is considered to be the most possible moving direction of the block.

Key words: block theory, removability, nonremovable block, vector method, stability