Overlying sand-inrushing mechanism and associated control technology for longwall mining in shallow buried coal seams with the soft surrounding rock

Taking the sand-inrushing accident of the Selian No. 1 coal mine in the Ordos of inner Mongolia as the research background, four main factors of sand-inrushing, including sand source, channel, sand-breaking power, and flowing space, were analysed. The disaster formation process (SCPS) illustrated that sand-inrushing disasters in shallowly buried coal seams with soft surrounding rock have the characteristics of being significantly influenced by mining, the development of vertical overburden channels, and sufficient space for water-sand mixed particles to flow. Universal Distinct Element Code (UDEC) software has been used to reveal that the vertical cracks in the overburden between the coal wall and support undergo a process of development and expansion along with the cumulative stress of mining. This showed that the vertical fissure through the overburden is the main pathway for the disaster. Combined with the site conditions, disaster occurrence mechanism, and numerical simulation results, a comprehensive prevention and control technology based on the working face and roadway grouting to block the channel was proposed. It contains reasonable mining height and optimisation of advancing speed, so that safe and efficient mining of coal seams in shallow-buried soft surrounding rocks could be achieved.