Comparative impact of mining activities on groundwater flow field between the wet and dry seasons in abandoned coal mines

Understanding the seasonal variations of the underground water flow field in abandoned coal mines is of great significance for regional groundwater dynamics analysis and environmental assessment. This study takes an abandoned coal mining area in Zhangqiu District as the engineering background and established a numerical model of the groundwater flow system, aiming to explore the seasonal variation patterns of the underground water flow field in closed mining pits. The results show that The hydraulic gradient in the south is larger, and the hydraulic gradient in the north is smaller. When the mine is closed for 5 years, the groundwater flow field in the southern part of the study area has little change during the wet and dry seasons. The highest water level in the wet and dry seasons in the northern part of the study area reaches −6 m, but the regional water level of −42 m in the wet season is significantly larger than that in the dry season, which may be due to the lag in rainfall replenishment of Ordovician karst water. The groundwater flow field of Ordovician karst water in the study area is basically unchanged after 10 years of mine closure, forming a near-stable groundwater flow field with the overall flow direction from north to south. But the groundwater level decreases obviously and it is suggested to reduce the exploitation amount.