Dynamic structural evolution of overlying strata during shallow coal seam longwall mining

Wang et al discuss the typical characteristics of the coal seams include shallow burial depths, thin bedrocks, and thick unconsolidated quaternary layers. It has also been observed from practice that roof step-form subsidence and chock closure failure disasters often occur during the weighting periods. If the mining activities induces severe roof step-form subsidence, coalescence of open cracks along the palisades may occur, with the consequent formation of penetrating passageways through which water and sand may rush in, resulting in a water and sand inrush disaster on the working face. Coal mine roof disasters constitute serious safety threats in mining practice. Incomplete statistics show that 12 support failure incidents have occurred since 2007 in the Shendong shallow coalfield longwall mining area.