Research on the mechanism of hidden disasters and control technology for collapse columns

Collapse columns with complex characteristics are often encountered in coal mining, making it essential to analyze their disaster-causing mechanisms and control measures. Based on a collapse column exposed at the 2303 working face of the Guotun Coal Mine in Shandong Province, geophysical exploration and drilling were carried out to identify its characteristics and hidden hazard factors. The results show that: the collapse column exhibits a vertically penetrating funnel-shaped structure, with a major axis of 83 m and a minor axis of 78 m. Its bottom connects with the third limestone aquifer (referred to as the "Third Limestone") of the Taiyuan Formation, forming a water-conducting pathway characterized by a "water-filled floor fracture zone-karst fissure-mining-induced fracture" system. The hidden hazard factors of the collapse column include fragmented fillings within the column, penetration through the roof and floor strata, and inherent water conveyance and normal water storage capacity. Using the discrete element method, the disaster-causing mechanism was analyzed, and a control scheme was proposed. The collapse column induces two types of hazards: it serves as a water inrush channel for the Third Limestone aquifer in the floor, leading to floor water inrush disasters; meanwhile, the fragmented rock mass within the column can trigger roof collapse. The implemented control scheme involved grouting reinforcement in the floor of the geologically anomalous area, the Third Limestone aquifer, and the roof and floor strata. This achieved a grout diffusion radius of 15 m, a water-blocking efficiency of 98.7%, and a reduction in water inflow from 150 m³/h to 2 m³/h. Post-treatment characteristics—namely the reduced water inflow from the Third Limestone aquifer, grout leakage in the belt haulage roadway, and significant floor heave without grout leakage—confirmed that the collapse column was fully reinforced. This study provides a reference for solving similar mining-induced geological hazard problems.