Study On Aquifer-aquifuge Structure Variation And Water Resources Dynamic Evolution With Large Scale Mining In Northern Shaanxi Province

The coal resources have characteristic of shallow buried, large thickness and richreserves but short water source and vulnerable environment in semiarid-aridnorthwest China. With strategic westward shift of coal exploitation more quickly inChina, the contradiction between coal mining and water protection show morespecially. Therefore, taking Shennan Coal Area located in the border area of eastMaowusu desert and loess plateau as research objects, based on hydrogeology survey,the hydrogeologic and engineering geologic condition also with its mining variation,variation types and distribution of aquifer-aquiclude strata structure, as well as thewater resources dynamic circulate process with shallow mining have analyzed byexploration and situ tests, indoor tests, numerical simulation, model similar simulationtests, rock-soil mechanics and underground water dynamics theoretical analysis aswell as field observation methods etc. And the new water preserved mining methodhas proposed, which is using of water storage by goaf for water supplying. Innovativeresults of this dissertation have been displayed as follows:(1)By a lot of additional hydrologic geology explorations, the hydrogeologiccondition and water resources present status in research area have investigated.Relative abundant sand dive recharges river system steadily in Shennan Coal Area,and the river basin supply water for the vegetations, so the "sand dive recharge-riverbasin" entironment is proposed for preventing mainly.(2)The Lishi and Baode Ground loess permeability and its variation characterswith mining have analyzed by variable head permeability tests, X-ray diffraction tests,expansion tests, triaxial infiltration tests, water injection tests in pit and situ water pressure(injection) tests. The results show that Lishi and Baode Ground loess layers arerelative aquifuge of sand dive before mining, and it is the key of water preservedmining. The permeability and its recovery character after damage of the two loesslayers have researched with different effect degrees including connected fissures area,pull apart area, central press area and whole move area. The whole residual thickness ofresisting-water loess layer beyond40m has proposed for protecting the overburden sand dive fromdry.(3)Three main mining relevant factors of sand dive aquifer-aquiclude structurevariation have analyzed for quantization in study area. Based on that, theaquifer-aquiclude structure mining variations are divided as three, including seepage flow variation type, leakage flow variation type which contains overrun leakage flow variationtype and limited leakage flow variation type, subsidence variation type which contains limitedsubsidence variation type and overrun subsidence variation type. The hydrological geologycharacters and significances of five aquifer-aquiclude structure mining variation types haveanalyzed. Seepage flow and overrun leakage flow variation types make water resources leakage.Limited leakage flow and limited subsidence variation types make water resources fluctuation.Overrun subsidence variation type makes water concave dry.(4)Based on the dynamic fluid-solid coupling physical simulation tests andunderground water dynamics theoretical analysis,mechanism of sand dive leveldynamic process affect by aquifer-aquiclude structure limited subsidence and limitedleakage flow variation has analyzed. The calculation methods of sand dive level drop and dynamicrecovery process have proposed. And the sand dive level recovery finally needs1a withaquifer-aquiclude structure limited subsidence variation in research area. The mining practicehas checked the analysis result. At last the response characters of entironment in waterfluctuation area have analyzed and countermeasures have proposed for preventingenvironment.(5)Based on analysis of water resources circulate process characters withaquifer-aquiclude structure mining seepage flow and overrun leakage flow variation, waterresources recharging conditions, water resources storage characters, water storagemaximum and dynamic process by goafs are researched. A new model which is usinggoafs for water resources storage and exploiting it for water supplying has proposed.And the practice checks the new model from technological, economic and ecologicalviews.(6)Based on hytdrological geology characters with different aquifer-aquicludestructure mining variation types, the water resources effect with first coal mining inShennan Coal Are have appraised. The water resources distribution in the end of2015has forecasted. Some proper water preserved mining technical measures haveproposed, which have coordinated coal mining and water protected successfully.