Study On Strata Behavious Characteristic And Control Technology Of Hard Roof In Ba Coal Mine

In the process of coal mining,coal seam hard roof is one of the main disasters in coal mine accident.Hard roof of stope is close distance will lead to a large area of hanging roof,a large area of hanging roof sudden falling impact dynamic pressure,cause harm to the equipment and staff,to bring great hidden trouble to the safe production of coal mine.In deep mining environment,the high ground stress makes the hard roof strata pressure problem particularly prominent.Therefore,it is of great significance to study the characteristics of the pressure manifestation characteristics of hard roof.In this paper,the laws of roof breaking in the mining face are studied by means of field investigation,laboratory measurement,theoretical analysis and numerical simulation.Through the analysis of the geological condition and the rock pressure appearance of the Ba coal mine,it is concluded that there are many hard roof plates above the 3-1 coal seam,and the ground pressure appears frequently when the roof is collapsed and pressed.Through the hard roof breaking theory analysis and numerical simulation analysis of FLAC3D,it can get the hard roof first caving step distance and periodic caving distance in 311103 working face,and different position of working face pressure characteristics analysis.Based on the theoretical calculation of roof pre splitting blasting parameters,combined with the actual situation in the field,the layout scheme of roof pre splitting blasting for the 311103 working face is determined.The results show that:the hard roof first caving step distance of 311103 working face in Ba coal mine is about 55m,periodic caving distance step distance is about 37m,the class of main roof belongs to IVb.At the same time because the roof pressure is very strong,it should take same measures to control the roof collapse step on a reasonable distance,to reduce the roof compression strength.The roof pre splitting blasting method is applied to the 311103 working face to shorten the roof caving step and to test the effect.Through monitoring the working resistance of the hydraulic support,the first step pressure of the roof is 30.9m,and the period is 24.7m.And the process of mining mine pressure appear smooth,roof pre splitting blasting and weakening effect is good,to ensure the safety of coal mining face.