Analysis And Evaluation Of The Influence Of Coal Mining On Shallow Groundwater System

The large-scale development and utilization of coal resources often destroys aquifers and triggers a series of hydrogeological and environmental problems.It is of great significance to analyze and evaluate the impact of coal mining on the groundwater system for the protection of groundwater resources in mining areas.This article takes Wulanmulun and Liuta coal mines as examples,based on the basic theories of coal field geology,hydrogeology and environmental science,through field investigation,monitoring,analytical calculation and other means to discuss the mechanism of coal mining on the groundwater system.The influence process and dominant factors of coal mining on groundwater power field and groundwater chemical field are analyzed,and multiple groundwater environmental element indicators are selected to construct a groundwater environment safety index system,and the groundwater environment safety during the mining process in the study area is evaluated.Through the above research,the following conclusions are drawn:(1)Based on the empirical formula of "three underground coal mining",Tangshan Branch and China University of Mining & Technology-Beijing,the height of the caving zone and the water conducting fissure zone caused by coal mining in the study area is calculated.The caving zone near some boreholes has exposed the 1-2 coal overlying aquifer,causing the shallow groundwater level to drop or the formation of goaf,and the transformation of surface water and groundwater The relationship also changed,and the flow of gongnieergai ditch decreased or even dried up.(2)The spatial analysis function of GIS is used to analyze the temporal and spatial variation law of water level in the study area.The groundwater level shows a significant downward trend from 2011 to 2018,with a water level drop between 1.14-8.47m;the groundwater level drop in the study area gradually increases from south to north.On the basis of equilibrium analysis,the influence of precipitation and coal mining on groundwater level is quantified by multiple regression model.The main reason for the continuous increase of groundwater level is the increase of water inflow caused by the continuous increase of coal mining and the destruction of aquifer.(3)Analyzed the coal mining of groundwater in the field of mechanism,the influence of the concentration of fluoride in ground induced by coal mining are increased,in addition,thestudy area overall total e.coli,nitrate,ammonia nitrogen concentration is obvious downtrend,chloride,oxygen consumption,iron,manganese concentration steady fluctuation trend on the whole,most of the water quality indicators of the evaluation results in ? and ? class under the water,the most polluted in 2011.(4)The groundwater environmental security index system was constructed,including nine indexes,such as precipitation,subsurface runoff depth,drought index,COD concentration,sulfate concentration,ammonia nitrogen concentration,fluoride concentration,accumulative annual change of groundwater level,and pollution diameter ratio.The analytic hierarchy process and entropy method were used to determine the weight value.The evaluation results showed that except 2014 and 2016,the groundwater environment was in an unsafe state,and the rest years were in a basically safe state.Finally,the paper puts forward some measures to ensure the groundwater environmental security from the aspects of establishing and perfecting water management institution and water management system.