The Effect Of Complex Hydrogeological Structure On The Controlling Of Water Inrush Of Roof And Floor In Litang Coal Mine

The traditional evaluation theories and methods for water inrush forecast simply process aquifuges, which did not considered the influence from the complex hydrogeological structure on water inrush and failure zone in roof and floor. After the theory of water-resisting key strata was proposed, there are significant meanings in theory and practical application to conduct the thorough research that studying the influence from the complex hydrogeological structure on water inrush and failure zone in roof and floor.Taking the Litang coal field which located in the northwest of Xuzhou, Jiangsu province as an example, studying the control effect on water inrush by complex hydrogeological structure. Depend on drilling, dewatering test by stages, probe for strata structure, water quality analysis, physical-mechanical strength test of rocks and etc to find out the hydrogeological condition and engineering geological condition in this region, also analyzing the the water-resisting property of its roof and floor based on the theory of water-resisting key strata, methods that to divide the water-resisting key strata structure model had been put forward. FLAC3 D is used to simulate the mining failure law in the roof and floor, and contrastively analyzed the influence on the risk of water inrush, both are based on the influence of the structure of water-resisting key strata. Relevant waterproof measures are proposed. Get the main knowledge as following:(1) The structure in Litang is complex, mine field were separated into different blocks by faults, but the boundary fault is a water-resisting layer, which limiting the lateral recharge; Vertical supply of aquifers was controlled by complex aquifuge structure of 9-2 coal seam roof and floor, all the aquifers in the coalfield showed a weak water abundance, and no hydraulic connection exist between them.(2) The properties of different blocks are variable, some with lower strength of mudstone and better water-resisting property; while in some parts, the mudstone has a larger strength, but These fractures will sealing when encountering water, still possess the water-resisting property, Depend on these, we thought that the strata structure in roof and floor conform to the features of soft and hard alternated water-resisting key strata.(3) Based on the theory of water-resisting key strata to present the water-resisting structure model. The structure in second and third mining areas: three layers of soft rocks and hard rocks are alternatively in the roof and five layers of both are alternatively in the floor; while in first mining area: two layers of soft rocks and hard rocks are alternatively in the roof and the structure of floor is same with second and third mining areas.(4) Utilizing FLAC3 D to simulate the influence that water-resisting key strata exert on mining failure in roof and floor. The simulation results showed that in first mining area, the ranges of roof failure are 26.7 meters and the depths of floor failure are 16.3 meters; while in second and third mining area, they are 29.8 meters and 6.8 meter; Has the obvious difference according to the empirical formula, the analysis suggests that in water-resisting key strata, soft and hard alternated complex hydrogeological structure has different control effect to Mining Failure.(5) Based on the comparative evaluation on the risk of water inrush result, Considered the water-resisting key strata has control effect to mining failure, Part of the region has apparent change.