General pyramid method for removability analysis of concave blocks in fractured rock mass and its engineering application

The sudden collapse or sliding of concave blocks under external force interference may cause the overall or local instability of engineering rock mass, and then cause serious casualties and economic losses, making the removability analysis of concave blocks become the focus of rock mechanics research. In order to analyze the removability of concave blocks in fractured rock mass, the basic assumption of traditional block theory is improved from the aspect of joint finiteness, and the generalized expression of block pyramid is established. Using the graphical method, it is analyzed that the finiteness and removability of the concave block can be characterized by its block pyramid and joint pyramid. The relationship between the block pyramid and joint pyramid of concave block and its finiteness and removability is derived and verified. A general pyramid method (GPM) for analyzing the removability of concave blocks in fractured rock masses is proposed. Based on the GPM method, a block analysis and identification algorithm is developed. Finally, the engineering application of GPM method is carried out with the roadway roof in two test areas in Tongkeng Mine in Guangxi. The results show that the GPM method can effectively predict the block type of the concave blocks on the roadway roof, and ensure the safety and stability of rock mass engineering. Compared with the traditional block theory method, the GPM method can be applied to the block type analysis of concave blocks, which has important theoretical significance and practical value for improving the rock mass stability analysis method.