Status analysis of the key parameters of blasting borehole and the retaining effect for gob-side entry retaining by the way of roof cutting and pressure releasing

Abstract：The technology of gob-side entry retaining by the way of roof cutting and pressure release is an active pre-cracking and pressure releasing technology without coal pillars.This technology has more higher performance price ratio, simpler process and faster entry retaining compared with the traditional entry-side filling technology, and has been developed rapidly in recent years.The application statuses of more than 30 coal mine areas were summarized in China.The key parameters of roof cutting borehole, such as cutting depth, cutting angle, cutting borehole diameter, space, and so on, were statistically analyzed, and the effect of gob-side entry retaining was also analyzed.The results showed that the current technology of gob-side entry retaining by roof cutting has been widely used in thin-and medium-thick coal seams with 0.9～3.5 m thickness.The heights of roof cutting were 1.8～20 m, and the angles of roof cutting were 0°～20°.The spaces of roof cutting between the cutting boreholes were 200～2 000 mm, and the diameters of roof cutting borehole were 32～80 mm.The influence range of the gob-side entry retaining by mining dynamic pressure was 20～280 m.The successful experience and some problems in application of the remaining entry were summarized, which provided an important engineering reference for promoting gob-side entry retaining by roof cutting.

Keyword：roof cutting and pressure releasing;gob-side entry retaining;key parameter;blasting borehole;directional blasting;