Parameters design and engineering application of directional blasting for roof cutting pressure relief of waterproof coal pillar
Aiming at the stability protection of the waterproof coal pillar adjacent to the fault in the coal mine,the design and application of directional blasting parameters was studied for the roof cutting pressure relief of waterproof coal pillar,with the engineering background of the 3309 working face in Hebi Zhongtai Mining Industry.By comparing and analyzing the support pressure distribution of the waterproof coal pillar before and after the roof cutting,the mechanism of directional blasting was revealed.When the roof of the goaf collapses,the large cantilever structure is cut off and then collapses rapidly,and the lateral support pressure above the waterproof coal pillar rises slowly,and then extends to the depths and slowly decreases to the in-situ stress.FLAC3D and ANSYS/LS-DYNA software were used to establish different uncoupling coefficient directional energy blasting models,and the numerical simulation results showed that the peak stress after roof cutting was reduced by about 27.8%,and the distance between the peak position and the coal pillar rib of the 3309 working face was obviously increased,which improved the stress environment of the area near the working face air return way.Comprehensively considering the slitting effect and explosives utilization rate,the optimal charging structure of the normal section was determined by the uncoupling coefficient of 1.7;according to the results of numerical analysis and the distribution of faults,systematic differentiated blasting parameter design was carried out for the air return way of the 3309 working face,and the field application showed that the effect of directional blasting was favorable for the roof cutting pressure relief,which was effective to protect the waterproof coal pillar.
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