Thick seams tension relieving measures - using incline holes drilled from bottom bench to seam floor and filled with explosive

摘要

Test bore holes are driven in a slightly downwards inclined direction from the coal face (41,42) in the lower bench (16) of the seam and are terminated near the seam floor (13). When critical solid results arise, additional loosening shot firing bore holes (3,30,31,6,60) are driven in the floor (19) in a steeply inclined direction towards the waste side of the face. The test and shot firing bore holes are filled in their bottom end with an explosive. The explosives of adjoining rows of bore holes are then detonated together at equal time intervals. Before the explosives the bore and shot firing holes are infused with high pressure water with added calcium chloride.