Assessment Of Water Richness Of Aquifer In Lower Group Of Thick Loose Layer And Study Of Safe Coal Pillar Setting-up

In recent years,mining under loose aquifer has gradually become one of the hot issues of shallow resources development.At present,the research work of mining under thick loose aquifer is mainly concentrated in Yanzhou,Huainan,Zaoteng and other mining areas in North China.Water-rich of thick loose aquifer in shallow coal mine is very important to the safe production of mine.Therefore,the research on water-rich law of thick loose aquifer and safe coal pillar setting is not only the deepening and perfection of the related theory of loose aquifer,but also the development and supplement of mining theory under special conditions.Taking Baodian Coal Mine in Yanzhou Mining Area as an example,the following research work has been carried out on the characteristics of loose soil,the law of water enrichment in loose aquifer and the problem of setting up safe coal pillars in coal seam mining under the condition of thick loose layer deposition.(1)The sedimentary characteristics of thick loose stratum in Yanzhou mining area are obviously regional compared with other thick loose stratum mining areas.Lower Quaternary loose stratum is the main dangerous source affecting coal seam mining.The suction characteristics,stress characteristics,strength characteristics and permeability characteristics of soil in loose stratum are analyzed theoretically.The seepage of loose aquifer is divided into natural seepage and mining seepage,and natural seepage.Flow obeys Darcy’s law,and mining seepage is divided into indirect sweep and direct sweep.The corresponding seepage characteristics are given according to the different fluid flow patterns in mining affected areas.(2)Based on the analysis of regional geology,hydrogeology and borehole exposure data in the south of No.6 mining area of Baodian Coal Mine,it is considered that the bottom aquifer of the lower quaternary group is the key aquifer affecting coal seam mining,and its water level is decreasing year by year.The clay content in the stratum can effectively reduce the permeability and water-rich of loose sandy soil.Through Kriging space interpolation method,the distribution of aquifer thickness,sand-clay thickness ratio,flushing fluid consumption,core recovery rate and permeability coefficient at the bottom of the lower quaternary formation in the study area are analyzed.A discriminant analysis model of aquifer water-enrichment at the bottom of the quaternary system is established by Fisher discriminant analysis method.Finally,the variation rule of aquifer water-enrichment with time is considered,and the research results are obtained.Water-rich of bottom aquifer of regional quaternary lower formation is very weak to weak.(3)Using the discrete element software UDEC to simulate the deformation and failure characteristics of overburden strata under thick loose seam mining under different bedrock thickness and mining technology conditions under regional geological conditions,eight schemes were established to study the influence of bedrock thickness change,stratified fully mechanized mining,fully mechanized caving mining and fully mechanized caving mining under the net on the deformation and failure characteristics of overburden strata by controlling single factor change.(4)According to the technical conditions of mine mining,comprehensive theoretical calculation formula and Yanzhou empirical formula,and analogous numerical simulation results,determine the height of overburden caving zone under the conditions of fully mechanized mining,fully mechanized caving mining and fully mechanized caving mining under the net,and finally get the safe and reasonable height of sand control coal pillar,and formulate a reasonable mining plan.