Abstract:
Yushen mining area is located in an arid and semi-arid area,and its ecological environment is very fragile.Drainage is the main method to prevent and control the roof water disaster in Yushen mining area.Excessive drainage increases the burden of mine drainage.In addition,it is not conducive to protect the shallow groundwater resource.Therefore,under the prerequisite of preventing and controlling water hazards,it is an important subject in water-decrease mining to calculate the pre-drainage residual water head,and determine the amount of water leakage of Quaternary unconsolidated aquifer during pre-drainage and mining,in order to minimize the amount of water leakage of Quaternary in the working face.Taking Jinjie coal mine as an example in this paper,based on the analysis of the occurrence characteristics of aquifer and aquiclude,two water filling modes of coal mining were established.Furthermore,the water-abundance of roof aquifer was divided.Based on the measured data of mine water inflow,the changing rule and component proportion ratio of water inflow were analyzed.The inner boundary of multiple working faces of continuous mining was described by drain boundary,and the numerical model of groundwater flow under excavation disturbance in Jinjie coal mine was established.The change rule of the amount of water leakage in Quaternary unconsolidated aquifer under different pre-drainage residual water head conditions of two water filling modes was studied,and the pre-drainage ending standard of working face was determined.The result showed that the coal seam roof of Jinjie coal mine was a typical sand-soil-bedrock structure.The main water filling source was entirely consisted of bedrock water.The water filling mode mainly included two modes:the water filling mode of weathered bedrock without soil layer missing,and the water filling mode of weathered bedrock with soil layer missing mixed with unconsolidated formation.The GIS multi-information fusion technology was used to divide the water-abundance of mine field,and the result showed that the relatively strong watery zone in the mine field was located in some sections of the second panel,the third panel and almost all the sections of fourth panel,which was basically consistent with the actual situation on site.The variation trend of drainage water quantity was basically consistent with that of mining water inflow curve on working face,each accounting for 50% of total mine water inflow.By means of numerical model calculation,the pre-drainage ending standard of working face under two water filling modes was determined to drain the water head until water-filled aquifer was 15 to 20 m above the coal seam floor,a certain residual head can be retained for mining without further drainage.By this time,the amount of water leakage in Quaternary unconsolidated aquifer reached the minimum value,which can play a role in reducing water while mining.The research result provides a new idea for “water-decrease mining” for shallow coal seam in Yushen mining area.