Influence of adjacent undercutting line positions on surrounding rock stability in block caving

In the block caving mining method, deformation and collapse can occur in roadways due to vertical stress concentration in front of the undercutting line. Therefore to better understand this behavior, we establish a mechanical model of two neighboring solidly-supported and two neighboring simply-supported stepped bottom space structures based on the theory of elastic plates. From this we derive an approximate analytical formula of the bending deflection function and an expression of the stress distribution using the Rayleigh-Ritz method. This mechanical model is applied to control the stability of perimeter rock near the undercutting advancement line in the Pulang Copper Mine in China, and optimize the positional relationship between adjacent undercutting advancement lines. The results indicate that both a larger misalignment between adjacent advancing lines and a closer spacing of the undercutting roadways significantly reduce the stability of the surrounding rock. The results of this study provide theoretical support and methodology for undercutting planning in block caving.