Vulnerability Evaluaiton Karst Groundwater In Ordovician Limestone Under Coal Mining Condition

Groundwater vulnerability evaluation is main method for effectiveprotection,national development and scientific management of groundwaterresources. It can not only reveal the environmental condition of regionalgroundwater, but also distinguish groundwater vulnerability degree in differentregional and judge the potential possibility of groundwater pollution.Based on the physical geography, geology and hydro-geological conditionsin the study area, the paper studied the groundwater environment under thecondition of coal mining,the relationship between the mining and karstgroundwater environment and Ordovician limestone karst groundwatervulnerability evaluation under the condition of mining are studied.There are many methods of groundwater vulnerability assessment atpresent.In the light of considering subjectivity and objectivity of weight, theEW-AHP-SIM evaluation system on the combination of entropy method,AHPmethod and comprehensive index method is established.,considered4factorsincluding the aquifer(A),the geological structure(G), aquifuge(A) and mine pressure destructive effect(M),which are considered In the process of evaluation.The Ordovician limestone karst water vulnerability index system AGAM undercoal mining is formed by four factors. In view of the situation of the studyarea,selected8parameters from the4factors as the evaluation indexes,theweight and vulnerability index are calculated.Using GIS software make spatialanalysis about8indexes thematic map, combined with the vulnerability index,obtained Ordovician limestone karst groundwater vulnerability zoning mapunder mining.The evaluation results show that:①Coal seam floor water pressure,subsided column distribution and effective aquifuge equivalent thickness havelarger composite weight of Ordovician limestone karst groundwatervulnerability assessment indexs, under2#coal seam and10+11#coal seammining conditions, respectively0.2712,0.2449,0.1536and0.2550,0.2649,0.1351. It shows that the three evaluation index are the greatest sensitive factorsof Ordovician limestone karst groundwater vulnerability under mining.②TheOrdovician limestone karst groundwater vulnerability evaluation including fivelevels are the lowest vulnerable area, lower vulnerable zone, moderatevulnerable area, higher vulnerable area and the highest vulnerable area. In2#coal seam mining the area respectively are85.77km2,10.73km2,6.83km2,4.67km2and0km2.In10+11#coal seam mining the area respectively are37.04km2、26.30km2、20.51km2、16.69km2and7.46km2.In space, thegroundwater vulnerability from the middle to both sides in the research area exists increasing trend. In the mining depth,the influence of lower coal groupmining is much larger than the upper coal group mining.The study region in the runoff area of Guo Zhuang spring area,the resultshas practical significance to prevention and control of mine water,protection ofwater resources and comprehensive utilization,and the coordinated developmentof regional economy and society in the domain.It also can provide the beneficialreference for other mining area.