Fluid-solid Coupling Experiment Research on Water Flowing Fracture Development Laws in Overburden Rocks of Shallow Buried Short-distance Coal Seams

In order to find out the mechanism of water flowing fracture development in overburden rocks of shallow buried short-distance coal seams, the solid-liquid coupling simulation experiment has been designed to analyze the mechanism during mining and the healing features of the water-resisting layer. In the mining process of lower coal seam, the water flowing fractures, which have been compacted steadily after the mining of upper coal seam in overburden rocks, will regenerate with different levels in different mining regions. The fractures' development and its water swelling in mining-induced water-resisting layer is synchronised to each other. Fractures in the mining boundary of water-resisting layer can heal under the influence of water swelling while the upper coal seam is mined. By the contrast, fractures in lower coal seam can not heal due to the lack of water swelling capacity. Fractures in the middle of water-resisting layer of goaf can heal under the mutual function of rock rotary extrusion and the swelling of water-resisting layer.