Research on Pillarless Mining Techenique by Top-cut Pressure Relief of Hard Roof

In order to solve the potential safety problems of high roadway drivage ratio, serious coal resources waste and the strss concentration in coal pillar mining in Tangshangou Mine, study was carried out in this paper on some key parameters such as the top-cut height, the top-cut angle and the blasting hole spacing of the pillarless mining technology by top-cut pressure relief of the hard roof through the numerical simulation and on-the-spot tests. The numerical simulation results showed that the bilateral cumulative blasting technology can play the roof pressure relief effect, and with the increase of the top-cut height, the top-cut pressure relief effect became more obvious; the cut slot has an obvious angle effect, which can not only affect the caving of the gob roof, but also affect the distribution of the stress concentration zone. The field blasting tests showed that when the hole spacing was 600 mm, the penetrating effect of the blasting hole was the best, and the damage to the surrounding rock was minimum. Under the conditions of the top-cut height of 6 m, top-cut angle of 15° and hole spacing of 600 mm, tests were carried out in the gob-side air-return way drivage of 8820 working face in Tangshangou Mine, and good results were achieved.