The Study Of The Construct Variation Of The Aquifer Under The Circumstance Of Group Mining In Typical Coal Mine In Changzhi Basin

Nowadays,coal resources have been explored seriously and widely.And this action has negative effects for groundwater,especially in the arid regions.Coal resources exploitation would aggravate crisis of water resources.Coal mining should not only guarantee the safety during produce and prevent water inflow,but also protect aquiferous rock formation which has meaningful to water-supply.The basic reason of shortage and damage of water resource is structure variation of aquifer.This variation finally would infect the region groundwater cycle and water resources would be polluted and drainage.The previous related work focused on the mechanism of prevention of water burst of roof,and neglected some aspects,such as,dynamic evolution regulations of mining-induced fractures,aquifer structure variation caused by coal mining and regional water cycle infected by mining.There aspects are important to declare character of water evaluation under the condition of coal mining.This article will finally declare the regulation of aquifer structure variation by studying the relation between inferior key strata and aquifer;evolution regulation of mining-induced fractures and aquifer structure variation under mining.The main conclusions are as follows:(1)The aquifer named K8 is the No.1 inferior key strata in the west of study area based the location of key strata and inferior key strata.The groundwater could infiltrate into goaf easily.The aquifer named K10 would be protected more than 1 inferior key strata.The K8 aquifer would be protected the key strata and inferior key strata in the other area;and the whole K10 aquifer would be protected by inferior key strata.Mudstone will swell reacting with water and form the relative aquifuge to protect aquifer.The thickness of the underlying mudstone of K8 aquifer in the middle of the area of Yu Wu mine and Chang Cun mine appeared low value range.The value of tendency of K8 aquifer is increased from west to east;the thickness of K10 aquifer is high value range in the north and south area and the value of tendency is more increased in the edge than in the middle.(2)The research object is a serious of rock that is part of coal seam under mining.In the statistical scale of 2 to 22,the box-counting dimension of the map is greater than 1.1,and the difference between any two maps is less than 0.3.So the fracture development satisfies the fractal conditions.Finally,we determined that this graph was fractal graphics and the graph of the distribution of mining-induced fractures is also fractal graphics.(3)The research rock is 0?24m away from open-off cut and 0?90m away from coal seam roof.We calculated fractal dimension and made fractal curve.Finally,we fined the relation between fractal dimension and distance of face-advancing demonstrated by the formula:D=-8×10-6L2+0.003L+0.933.Besides,the square of 10 cm×10 cm would be chosen as the whole range of growth of mining-induced fracture.We would study the fractal dimension and spatial-temporal evolution pattern of the square controlled.The result is that as the advanced of worked face,the fractal dimension of square had little change and waved nearby value of 1.(4)The software of Flac 3D would be utilized for deducing strain data in the range of growth of mining-induced fracture;determined relation between permeability coefficient and strain by studying different rock character;and calculated permeability coefficient mining rock.The permeability coeficient determined by water injection test in the inclined hole of S1202 well had been fitting with anotherpermeability coefficient determined by model of numerical simulation.We can conclude that these coefficients had high fitting degree and the correlation coefficient is more than 0.9.Rationality of numerical simulation would be proved and utilized to predict.The model have predicted 5 worked faces,they are S1201,S1202,S1203,S1204,S1205.The prediction showed that K8 aquifer and K10 aquifer will be destructed after mining.Finally,we can draw the distribution map of permeability coefficient of different distance away from coal seam roof.