| In the past few decades,with the continuous expansion of mining intensity and scale of Jurassic coal resources in northwest China,the problem of roof water damage has become increasingly serious,threaten the safety of coal production.The reasonable and effective prediction and evaluation of the water-richness of the roof aquifer is not only conducive to the comprehensive grasp of the water-richness distribution of the roof aquifer of the mine field,but also to make more scientific decisions.In this paper,a case from Jinjiaqu coal mine in Ningdong mining area was studied.It analyzes and quantitatively evaluates the geological structure in the mine field according to the geological data,hydrogeological data,drilling geophysical data and drilling(discharge)water test data of the mine field.Based on the method of set pair analysis-variable fuzzy set coupling evaluation,seven quantitative evaluation indexes are selected from the aspects of lithology and structure.This paper has achieved the following results:(1)There are 5 large and medium-sized main thrust faults,5 near equidistant folds and 44 small faults in Jinjiaqu mine field,among them,small faults are mostly those with a drop of less than 10m and dominated by normal faults.The fault strike is dominated by near NS and NE,and tends to be dominated by SWW and NE.Six structural evaluation indexes,including variation coefficient of slope of coal seam,intensity index of folds in horizontal direction,fault frequency density,fault scale density,fault number density and fault length density were selected to quantitatively evaluate the structure.(2)Using the formulas in the coal mining regulations and the empirical formulas in the adjacent mining areas,the development heights of the caving zone and water conducted fractured zone of the 2#and 3#coals in the study area were determined.The results showed that the height of water conducted fractured zone of 2c oal seamis bigger in the Midwest and northwest of study area,and that of 3#coal scam is bigger in center of study area.Moreover,the height of caving zone and water conducted fractured zone of coal seam 3#is greater than the upper minable seam spacing.And the change of coal caving zone height consistent with the change of the water conducted fractured zone.The sections of water-resistant strata in some exploration lines were drawn,respectively.It can be seen from the figure that the pore-fractured confined water aquifer of Zhiluo formation is widely distributed in the whole area with a large slope.There is no stable water-resisting layer.Thus,the whole Zhiluo formation is selected as the water-richness evaluation area.(3)Based on the lithological,tectonic and geological conditions,seven indexes including lithological index,variation coefficient of slope of coal seam,intensity index of folds in horizontal direction,fault frequency density,fault scale density,fault number density and fault length density were considered as the evaluation index of water-richness of the sandstone aquifer of Jurassic Zhiluo formation overlying the main coal seam.Set pair analysis-variable fuzzy set coupling method was applied to establish the water-richness evaluation model and reveal water abundance zones.The prediction results showed that the water abundance of Zhiluo formation can be divided into low and medium water abundance classes.The medium water-richness areas were mainly distributed in the middle and north of the study area and the east of the aeolian oxidation zone,while the low class of that were distributed in the south,east and west of the study area.And the evaluation results have better consistency with the unit water inflow in the drilling(discharge)water test data and maximum water inflow from mined working face. |
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