Micro-fracture Precursors of Water Flow Channels Induced by Coal Mining: A Case Study

The evolution of water flow channels typically includes a micro-fracture precursor, especially during deep mining. However, this precursor has not been well characterized. To get more insight into this precursor and its development, the no. 22517 panel in the Dongjiahe coal mine was studied using microseismic monitoring. The energy density of microseismic events was used to identify the spatial location and formation process of the water flow channels. Microseismic focal parameters, such as seismic energy, seismic potency, apparent stress, seismic moment, apparent volume, energy index, and the Gutenberg-Richter b value were determined for the micro-fracture precursors of the water flow channels. The cumulative apparent volume increased significantly and the Gutenberg-Richter b value decreased rapidly, corresponding to the micro-fracture precursor of the water flow channel. Based on the results, a Gutenberg-Richter b value of 0.7 may be an early warning threshold for the formation of a water-flow channel. Finally, a real-time early warning method for water inrush disasters in floor was established based on microseismic monitoring, geophysics, and the water inrush coefficient.