| The general characteristics of coal resources distribution in china northwest are shallow-buried, thick-coal-layer and ample. With the focus on exploration of coal resources transferring to the west, location of coal resources basement and abundant water resource has turned in a reverse distribution. Especially the Shendong and Shanbei coal basement which located in the border between inner Mongolia and Shanxi province is considered as modern exploration area due to large-scale, high strength and modernization of mining characteristics. The coal resources exploration activities have an inevitable influence on the underground water environment simultaneously. Therefore the groundwater resources issues and ecological environment destruction increasingly restricted the application in sustainable development strategy of "safety, sustainable, green, ecology" of the large coal base in china.Based on the field hydrogeological investigation, the comprehensive application of theoretical analysis, laboratory testing, computer simulation and other methods, this dissertation aims at the study of the coal base in the border area of Shaanxi Province, focus on the evolution mechanism and quantitative evaluation of groundwater environmental disturbance in the research area of coal resources development, in order to provide technical support and decision-making basis for the rational development of coal, scientific control, system construction in the west of China. The results of this research are listed as follows:1)The artificial coal mining activity is the basic reason of the structure system disturbance of the groundwater environment system. The dissertation puts forward the concept, structure, elements and functions of groundwater environment system based on the systematic analysis in the characteristics of water, coal, ring and the modern coal resources exploration. The concept of groundwater environment system is the system centre in modern mining area, which is based on the groundwater system and the groundwater resources and ecological value as the core system function. Human activities result in the weakening of the groundwater environment system and the loss of the water environment system. In addition, the groundwater environment system can be divided into three parts:structural system, hydraulic system and peripheral system, which is based on the space structure, range and function of the system; It is concluded that the hydraulic system is the direct cause of the environmental disturbance and evolution of groundwater in the general area, and the response of the hydraulic system is the fundamental reason of the evolution of groundwater environment system in the modern coal mining area.2)’Three belts and the zone’ is the main form of groundwater environment structure system disturbance. In this dissertation, the technological idea concludes the change of the stress and deformation of the damage and deformation of the medium permeability is studied. Starting from the additional stress state of the formation, summarizes the common relation between the tensile stress zone, compressive stress zone and tensile-compressive stress zone with deformation and damage of overlying strata. Analyzing the law of the typical overlying strata’Three belts and the zone(the caving zone, the fracture zone, the bending zone and the ground subsidence area). The damage characteristics of the overlying strata in different environmental conditions are well studied by using the similar materials simulation technology and computer numerical simulation technology.3) The law on permeability change in the process of rock deformation and damage. According to the indoor axial compression servo penetration test, it can be concluded that rock at the beginning of the force shrink more than 70%, in low permeability rock by consolidation deformation after the transition to cut fission form permeability in exploding point reduce about 50%, permeability during rock strain softening deformation increased more than 5 times at peak, after the plastic flow phase permeability stayed basic stable, the residual strength of permeability has increased about three times.4) The spatial extent of disturbance in the control structure system is the main aspect to reduce the leakage of groundwater. Using the groundwater dynamics analysis method, the common law can be concluded that, the larger area of overlying rock disturbance, the higher the height of the crack, the higher the permeability of the bending zone, the greater the groundwater pressure, the greater the amount of groundwater leakage.5) Quantitative study on the disturbance mechanism of "structural system" and "hydraulic system" in groundwater environment. The case study shows that:the permeability of rock mass increase by 15% while the permeability decrease by 3% in the surface subsidence basin; the 300m higher porosity of the coal pillar decrease by 10% relatively while the permeability of the overlying strata decrease by 26%. Underground mining space connected directly to the atmosphere, forming the " The free surface " of the underground water pressure and the water conductive crack zone. ’The free surface’ is the center of the water level of the funnel significantly, result in the increased vertical hydraulic gradient and flow rate. In the range 300m above the coal seam roof, the water pressure head is in the original state basically.6) Quantitative assessment of the degree of disturbance in groundwater environment system. Based on the numerical modeling of groundwater system, by using numerical process structure of mining disturbance variation factors(Three belts and the zone), it can be concluded that the water flowing fracture zone in boundary, bending belts about overlying strata permeability, the ground subsidence areas subdivision modeling process and then construct the quantitative evaluation model of groundwater environmental system disturbance. From the perspective of groundwater level, aquifer thickness and distribution of water balance, it is concluded the characterization of ground water environment disturbance degree evaluation index system.7) Case study on the quantitative evaluation of groundwater environmental system disturbance. Based on the technical thinking on underground environmental system disturbance model, establish the deep water rich pore and fracture of composite mine evaluation model and Shallow water rich loose pore type mine evaluation model. By simulation, it can be obtained the previous model directly reveal Yan’an bedrock fissure aquifer, aquifer formed the obvious landing funnel.due to the water conductive crack zone cannot connect the near surface loose porous water bearing rock series. The flow field in the loose aquifer is small, and the flow field is small, the maximum water level of the water drop is about 0.25m, and the water balance is slightly increased, and the loss of water resources is about 2040 m3/d. By drawing the EHe and the EHa equivalent index of the disturbance of the water bearing layer in the ecological disturbance, in the scope of recognition that EHe≥1, shows that some areas are ecologically influenced while containing water disturbance index Eha were less than 0.07, the water balance disturbance Eq index is 2.8%, including that the mine disturbance on the loose layer groundwater with minimal impact.The latter model:the formation of the hydraulic fracture of the excavation disturbed directly to the surface of the surface. Through simulation study, the top of the mining section has been obtained directly from the top of the mining area, and with the increasing of the mining area, the groundwater recharge is slightly increased, and the recharge increment is mainly due to the increase in the lateral direction of the area, the amount of water discharge and the reduction of the water evaporation. groundwater discharge volume increased significantly, the excretion of incremental is mainly due to the mining of groundwater to the mining section leakage excretion, resulting in the loss of mine groundwater resource,2012 mine groundwater resources loss reached 1.90 million m3/d. By drawing the EHe and the EHa equivalent of the disturbance index of the water layer, the results of the index of the EHe are more than 1.It shows that the water bearing stratum has been drainaged in a large scale, and the ecological damage is serious. The EQ value of water balance disturbance index also increases annually. It turns out that mining process have a negligible impact on the balance of water resource.8) Put forward the way of’Controlling water coal mining’.’Controlling water coal mining’ in modern mining area is carried out based on the different underground water environmental system, which shallow water poor fissured loess type coal mine for coal resource mining area or to encouraged mining areas while shallow rich pore water in the loose type mine for coal resources is restricted mining area, buried deep rich loose pore water and bedrock fissure compound filed for coal resources reducing subsidence control mining district.9) Mine water resource is the best choice to solve the problem of water shortage and environmental pollution in the study area. It can be concluded the principle in the water treatment of the sewage diversion and the quality of the water, and the way of the mine water reuse’, and the establishment of the regional mine water service company, to reach the mine water resources optimization allocation.In summary, this dissertation emphasizes in revealing arid regions of Western China coal mining disturbance caused by groundwater environment concept and connotation, exploration mining of groundwater system disturbance in the quantitative evaluation method, to provide scientific basis for control water coal mining technique and postharvest ecological restoration. |
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