Research On Water-richness Subdivision Method Of Coal Seam Roof Sandstone Aquifer In Yuanyanghu Mining Area

The sandstone aquifer at lower section of Jurassic Zhiluo Group in Yuanyang Lake mining area is the direct water-filled aquifer of 2#coal seam.According to the previous geological exploration and hydrogeological survey results,the aquifer’s thickness is uneven and between 0~382.65m with the average of 66.28m.On the other hand,the standard units-inflow is between 0.0027~0.2995 l/m·s with the average of0.0896 l/m·s and its hydraulic coefficient is between 0.0040~0.9557 m/d with the average of 0.1693 m/d.From all mentioned above,we can tell that this aquifer has the traits of thick layer,low permeability and poor water abundance.But in the process of construction and production,Maiduoshan and Hongliu coal mines happened serious roof water-inrush accidents one after another in 2009.09~2010.10 and 2014.07separately.In addition,according to the dewatering test at auxiliary transport lane of2#coal seam in Maiduoshan,there were 8 boreholes’water flow amount reaching at180 m~3/h and some even reached 240 m~3/h.In view of this very uneven water distribution,New research should be carried out as quickly as possible,which has an significant influence to the safety and efficiency for this two mines’construction and the orderly water prevention and control works.The research mainly took the two first mining areas of Maiduoshan and Hongliu mines as examples,basic geological and hydrogeological conditions were analyzed in detail through literature review and data collection.And on this basis:Firstly,sedimentary and structure features of the target aquifer were analyzed.Combining geological exploration data,10 factors were chosen and unnormal water-rich area under each factor was determined.With the result of previous pumping tests and the method of grey correlation analysis method,the correlation between each factor and units-inflow was calculated,which showed that lithological structure and thickness of middle-coarse sandstone had the relatively closer relationship with water abundance under sedimentary features.And fault fractal dimensional revised-index D_F and fold fractal dimension index D_f were two important factors with water abundance in structure features.Secondly,based on the multi-index comprehensive evaluation method,the indicators system of water abundance evaluation was established.With the manner of Water-richness index method,three constant weights including analytic hierarchy process(AHP),entropy weighting method,the combined and local variable weighting method were adopted to establish 4 evaluation models for water-richness subdivision.Ultimately,taking the actual water-inflow data of eleven working faces in the past of Hongliu first mining area as the criteria for water abundance checking,the results showed that the local variable weighting method was proved to be the best feasible approach.In addition,the relatively reliable mathematical relation between the water abundance degree and water inflow amount was established and tried forecasting the water inflow by stages and normal of three working faces in Maiduoshan mine’s first mining area.