Evaluation Of Impermeability In The Top Of Ordovician Limestone In North China Type Coal Field

To continue to promote economic progress, and with the growing demand for coal resources, the shallow and deep of North China coal have been mined on a group of increasingly scarce, the deep coal mining have become the inevitable choice of development to many coal mines. In addition to the flooding disaster at the top of the mined-out area, water bursting is the most serious problem in the deep coal mining. The general approach to solve this problem is to grout Face and area, reinforce bottom impermeability, and grooming reduced water pressure artificially. The natural impermeability of the top of Ordovician limestone hadn’t given great attention and been used. In fact, after the ancient crustal movement, Ordovician limestone top interface experienced a long period of weathering and erosion, formed some corrosion holes and cracks, but after a number of factors affecting, these karst space is filled with clay and other low permeability material, and after overburden compaction, this becomes rock which has a natural water-blocking ability. Therefore, understanding the performance of North China coal strata water blocking for solving coal mining group has an important significance.The evaluation of impermeability in Ordovician limestone top is set in Sangshuping coal mine of Hancheng Anthracite Mining Group, results are as follows:(1) Analyze the Geological data base and Hydrogeological data of the Mine, hydrogeology condition and impermeability of Ordovician limestone aquifer,Comprehensive research consider that the top of Ordovician limestone can be seen as relative aquifuge, meanwhile define the thickness of layer in this dissertation.(2) Comprehensive research about Geological background and geologic structure export a indicator system for evaluation of impermeability in the top of Ordovician limestone, including lithologic and structural, geological structure, drill core taken rate, fluid consumption,the degree of compaction and the thickness.(3) Based on Analytic Hierarchy Process(AHP) by using ArcGIS program, by defining resistance index, drawing profiles of index, evaluating weight of factors and superposing profiles, and then build evaluation system which reflect the consequences of factors.(4) Based on production practice by using natural breaks classification, evaluated the break points and divided impermeability regions which had an association with distribution structure. The evaluation result is satisfactory by testing with geological structures data and measured data of hole-drilling.