Instability mechanism and prevention technology of overlying rock structure in the mining of deep-buried coal seam free face
In response to the problem of instability of the overlying rock structure and induced impact disasters during the free face mining process of deep buried coal seams,taking Shilawusu coal mine as the background,theoretical analysis and on-site monitoring methods were used to deeply analyze the e-volution law of the overlying rock structure above the working face and the mechanism of mining in-duced impact.The preventive measures of overlying rock burst on the working face were put forward and verified on site.The results show that the maximum breaking step distance of the main key layer in the 221-08 working face during the solid coal mining stage is 186.54 m,and the maximum breaking step distance of the main key layer during the open face mining is 337.79 m.The low-level key layer changes from O-X breaking to high-level key layer X-O breaking;During the solid coal mining stage on both sides of the 221-08 working face,the spatial structure of the overlying rock presents a long arm F-shaped structure.When the working face enters the goaf for mining,the overlying rock structure changes from a long arm"F"-shaped structure to a long arm T-shaped structure.Due to the maximum breaking step distance of the main key layer during mining on the working face,it will gradually bend and sink under its own gravity,releasing a large amount of bending elastic properties and inducing the mining seismic phenomenon.The implementation of the blasting and top cutting method for the main key layer effectively converts microseismic events from"high energy low frequency"to"low energy high frequency",effectively reducing the frequency of mining induced vibrations in the mine,ensuring safe production on site,and providing theoretical reference for such mines.
long arm F shapelong arm T-shapeX-O structuregoafblasting pressure relief
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