Modeling Rock Fracture Propagation and Water Inrush Mechanisms in Underground Coal Mine

Water inrush in underground mines is a major safety threat for mining personnel, and it can also cause major damage to mining equipment and result in severe production losses. Water inrush can be attributed to the coalescence of rock fractures and the formation of water channel in rock mass due to the interaction of fractures, hydraulic flow, and stress field. Hence, predicting the fracturing process is the key for investigating the water inrush mechanisms for safe mining. A new coupling method is designed in FRACOD to investigate the mechanisms of water inrush disaster (known as "Luotuoshan accident") which occurred in China in 2010 in which 32 people died. In order to investigate the evolution processes and mechanisms of water inrush accident in Luotuoshan coal mine, this study applies the recently developed fracture-hydraulic (F-H) flow coupling function to FRACOD and focuses on the rock fracturing processes in a karst collapse column which is a geologically altered zone linking several rock strata vertically formed by the long-term dissolution of the flowing groundwater. The numerical simulation of water inrush is conducted based on the actual geological conditions of Luotuoshan mining area, and various materials with actual geological characteristics were used to simulate the rocks surrounding the coal seam. The influences of several key factors, such as in situ stresses, fractures on the formation, and development of water inrush channels, are investigated. The results indicate that the water inrush source is the Ordovician limestone aquifer, which is connected by the karst collapse column to No. 16 coal seam; the fracturing zone that led to a water inrush occurs in front of the roadway excavation face where new fractures coalesced with the main fractured zone in the karst collapse column.