Numerical and theoretical study of load transfer behavior during cascading pillar failure

Abstract

To further study the load transfer mechanism of roof–multi-pillar–floor system during cascading pillar failure (CPF), numerical simulation and theoretical analysis were carried out to study the three CPF modes according to the previous experimental study on treble-pillar specimens, e.g. successive failure mode (SFM), domino failure mode (DFM) and compound failure mode (CFM). Based on the finite element code rock failure process analysis (RFPA2D), numerical models of treble-pillar specimen with different mechanical properties were established to reproduce and verify the experimental results of the three CPF modes. Numerical results show that the elastic rebound of roof–floor system induced by pillar instability causes dynamic disturbance to adjacent pillars, resulting in sudden load increases and sudden jump displacement of adjacent pillars. The phenomena of load transfer in the roof–multi-pillar–floor system, as well as the induced accelerated damage behavior in adjacent pillars, were discovered and studied. In addition, based on the catastrophe theory and the proposed mechanical model of treble-pillar specimen–disc spring group system, a potential function that characterizes the evolution characteristics of roof–multi-pillar–floor system was established. The analytical expressions of sudden jump and energy release of treble-pillar specimen–disc spring group system of the three CPF modes were derived according to the potential function. The numerical and theoretical results show good agreement with the experimental results. This study further reveals the physical essence of load transfer during CPF of roof–multi-pillar–floor system, which provides references for mine design, construction and disaster prevention.