Stress Distribution Around Mechanized Longwall Face at Deep Mining in Quang Ninh Underground Coal Mine

Quang Ninh underground coal mines are currently in the phase of finishing up the mineral reserves located near the surface. Also, in this phase, a number of coal mines have opened and prepared new mine sites for the extraction of the reserves at greater depth. Several mines have mined at -350 m depth and are driving opening excavations at -500 m depth below sea level. The mining at greater depth faces many difficulties, such as a significant increase in support and excavation pressures. The longwall face pressure is mostly manifested in great magnitude that causes support overloaded and jumped and face spall/roof fall. This paper, based on the geological condition of the Seam 11 Ha Lam coal mine, uses the numerical program UDEC for studying the impact of mining depth on stress distribution around the longwall face. The results show that the deeper the mining is, the greater the plastic deformation zone is. The peak front abutment stress moves closer to the coal wall, mainly concentrating on the immediate roof and top coal. The top coal is greatly broken, and its bearing capacity is decreased. Some solutions to the stability of roof strata are proposed, and a proper working resistance of support is determined. Additionally, the paper suggests that the starting depth for deep mining in Quang Ninh underground coal mines should be -350 m below sea level.