Abstract: The lifting mode is one of the failure modes of finite movable blocks proposed by block theory. Although direct collapse is the most common failure mode in underground engineering, there is still a lack of suitable quantitative stability analysis methods, resulting in the scarcity of necessary theoretical support for the excavation and reinforcement design of underground engineering. To this end, an improved stability analysis method for rock blocks considering progressive damage is proposed. Main improvements include: introducing overload base and overload direction to quantify the reserve load; proposing two options of overload base which are Tan and Scal; and setting the overload direction on the boundary sector of the joint pyramid. The example verification results show that the improved method is fully compatible with the existing safety factor algorithm for the wedge failure mode. It realizes the quantitative stability analysis of the lifting mode. Finally, the stiffness assignment method and its sensitivity are discussed.

Key words: block theory, rock mass stability analysis, rigid body limit equilibrium, embedded mode, overload safety factor, overload base, overload direction