| 摘要 |
A blasting arrangement ( 10 ) includes drillholes ( 30 ) in a rock mass ( 20 ). Blind ends ( 32 ) are drilled to a desired level and, if necessary, are adjusted as shown at ( 62 ) to said level. Each hole ( 30 ) is plugged by means of a plug ( 42 ), which is protected by non flammable buffer material ( 44 ), at a level ( 40 ) spaced from the end ( 32 ). Explosive ( 50 ) is charged above the level ( 40 ) and the hole is tamped, shown at ( 60 ). The holes are detonated desirably by detonators ( 52 ), forcing the plugs ( 42 ) downwardly and compressing air in chambers ( 34 ) above the ends ( 32 ). The weakest part of each hole, around the end ( 32 ), is split causing a three dimensional zone of weakness at the level of the ends ( 32 ). Air forced into the zone of weakness causes a fracture zone ( 70 ) at that level, inhibiting propagation of blasting shock waves and protecting the material underneath the level of the ends ( 32 ). |
