Numerical Simulation Research Of The Influence Of Coal Mining To The Upper Aquifer

However the exploitation of coal resources has made a significant contribution to the sustainability and stability of the National economy, it affects even destroys the upper aquifers which closed to it. The reason is that the upper rocks of gob's roof lose support, then occurs collapse and cracks. the gobs of different depth of mining,different sizes were made by coal mining. These cracks become channels which groundwater resources of various types'aquifers above the gob leak down quickly. That makes the decrease of the groundwater reserves in the upper aquifers; even destroy the homeostasis and ecological environment. Therefore, the study of influence of coal mining to the upper aquifer has a great significance for protect the groundwater resources.Based on Jiuxin coal mine in Pianguan county, this article analyzed the condition about production of this coal mining and natural geographical situation, geology condition, hydrology geology condition. Thereby the writer generalized hydrogeology conditions and established Vertical one-dimensional flow mathematical model, and adopted the Finite Difference Method to simulate the underground flow by Visual Modflow software. This article analyzed the influence of coal mining to the upper aquifer by changing the thickness of the coal seam mining,the distance from coal seam roof to the bottom of upper aquifer and the permeability coefficient of water-resisting layer. The main conclusions obtained as follows:(1) In the situation of hydrogeological parameter constant, with increasing the thickness of the coal seam mining, guide water fracture zones growth altitude increased gradually, It arrived the Neogene System aquifer firstly, water level of aquifer fell rapidly, When mining thick is 6 meters, the aquifer was dried after 300 days. When mining thickness increase to 12 meters, Well-precipitation time advance to 120 days. Then fracture zones continued to develop with the increase of extraction thickness and extended to the bottom of the Quaternary aquifer, Aquifer affected. And flow speed of movement down accelerated, water level w continued to decline, and the aquifer was dried after 60 days.(2) In the situation of hydrogeological parameter constant and fixed extraction thickness of 4m, water level of aquifer declined gradually, when the distance of the roof of coal seam to the Neogene System aquifer was less than 50 meters, aquifer affected. In the distance of 30 meters, after 180 days, the Quaternary aquifer was dried. When the distance continues to increase to more than 50 meters, the water level just decreased in a small range in the whole simulation period, two aquifers were undraped.(3) In the situation of hydrogeological parameter constant and fixed extraction thickness of 4 meters, water level declined gradually increasing with the increasing of permeability coefficient, During the 300 days of simulation period, water level fell to the bottom of the Neogene System aquifer, this aquifer is dried. And the Quaternary aquifer was affected little, and the water level was less than 1 meter behind the Neogene System aquifer. In the whole simulation period, aquifer is part of the drainage.