Study On Height And Development Form Of Roof Water Flowing Fractured Zone Under Mining Influence

China has a vast territory and rich mineral resources.In terms of energy reserves,coal resources account for more than 90%,and coal resources account for more than 50% in the energy consumption structure.In recent years,with the increase of mining depth,the occurrence conditions of coal seams are becoming more and more complex,and a large number of coal mine water inrush accidents have occurred.Therefore,the timely and accurate prediction of the development height of coal seam roof fractured zone can effectively prevent the occurrence of roof water inrush accident.Taking the 1303 working face in the third mining area of Sima Coal Mine as the background,this paper predicted the developmental mechanism of the water flowing fractured zone through similar simulation test and numerical simulation analysis,and predicted the height of the water flowing fractured zone in the 1303 working face combined with the modified formula,and changed the lithology combination of the roof and the buried depth of the coal seam to study the development height and shape of the water flowing fractured zone under different working conditions.The conclusions are as follows:(1)Based on the three laws of similarity theory,similar simulation tests had carried out for different lithologic combination roofs and different buried depths of coal seams.Digital photographic measurement system was used to analyze the test results,and it was obtained that the shape of water flowing fractured zone of different models was trapezoidal,among which of hard rock lithologic roof model was an isosceles trapezoid.According to this model,the development height of roof crack conduction zone in the third mining area of Sima Coal Mine is 69.6 m,and the crack-mining ratio is about 12:1.(2)Through numerical simulation,the development height of the fractured zone in the third mining area of Sima Coal Mine is 80-96 m.In the two-dimensional numerical model,under the same parameters,the plastic zone morphology obtained by the strain-softening model is the same as the experimental results,and the shape of the water flowing fractured zone is an isosceles trapezoid.The fracture state of the rock layer at the top of the model is analyzed by using the fracture connection degree based on the plastic hinge theory.In the three-dimensional numerical model,the plastic zone obtained by Mohr-Coulomb model is in the shape of inverted trapezoid or pillow,while the plastic zone obtained by strain-softening model is in the shape of trapezoid.(3)The results obtained by using the empirical formula of fractured zone height in the current specification have a wide range.On this basis,considering the mining height,hard rock lithology proportion coefficient,working face slope length,advancing speed,buried depth,rock quality designation(RQD)and other factors,combined with similar simulation test and numerical simulation analysis,the error correction coefficient is introduced to construct a multi factor and multi method fractured zone prediction formula.Based on the prediction of the height of water diversion fracture zone in 1303 working face in the third mining area of Sima Coal Mine,the calculated development height of water diversion fractured zone is 105.5m.There are 38 figures,9 tables and 96 references.