Formation mechanism and prevention technology of water hazard from bed separation in hidden outcrop area of coal seam

In order to find out the water source, channel and formation mechanism of water damage in the coal seam working face in the hidden outcrop area of Songxinzhuang Coal Mine, we analyzed the changing law of water level in the aquifer, combined with the hydrogeological conditions of the working face and the characteristics of the water inrush, and preliminarily judged the type of the water damage in the roof to be the water inrush from bed separation. Numerical modeling was used to study the formation location, shape and height of the separation space in the hidden outcrop area of the coal seam under the mining conditions of the working face, and numerical modeling and on-site measurements were used to obtain the development height of water-conducting fractured zone after the mining of the working face. The research results show that due to the significant differences in mechanical properties and physical characteristics of the overlying strata of the coal seam, a bed separation space is formed at the angle unconformity contact position after the working face is mined. When the water-conducting fracture zone develops to the upper aquifer, groundwater seeps through the fracture network into the bed separation space for recharge, forming a bed separation water body. Under the combined action of the pressure of the overlying rock layer and its own gravity, this water body breaks through the lower aquiclude rock layer and rushes into the working face, ultimately resulting in bed separation water damage. Regarding this formation mechanism, it is proposed to implement comprehensive prevention and control measures such as conducting advanced drainage of the aquifer in the roof of the hidden outcrop area, controlling the uniform mining speed of the working face to inhibit the excessive development of the water-conducting fracture zone, optimizing the mining limit and reasonably reducing the mining height. These measures can effectively reduce the accumulation scale and collapse risk of the bed separation water body. Research shows that due to significant differences in rock layer strength in the hidden outcrop area of the coal seam, bed separation water disasters are prone to occur. The proposed prevention and control measures can provide theoretical basis and technical support for water disaster prevention in working faces with similar geological conditions.