Abstract: A drill hole (350) extends into rock to be blasted. A blasting accessory (310) includes a container portion (312) for holding a predetermined volume of stemming material, and a spacer (330) for spacing the stemming material a predetermined distance from a surface, e.g. a blind bottom of the drill hole. The container portion has a top (320) surrounded by a dilatable, inverted skirt forming a seal (342), and forms a support for a blasting substance like an explosive.

Abstract: 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).

Abstract: 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).

Abstract: A plug for use in a borehole, the plug including a body member of a flexible material, the body member defining a floor portion, with a wall portion bounding and extending from the floor portion for engagement with an inner wall of the borehole for sealing the borehole. The invention also relates to a method of supporting materials in a borehole.

Abstract: A plug device for absorbing the energy of an explosion generated during a blasting operation in a bore located in a rock formation including a cup-shaped member having an annular sidewall and a closure wall, the cup-shaped member being constructed of a yieldable material that allows the cup-shaped member to form a sealed engagement with the bore thereby forming a barrier to the explosive force, the cup-shaped member includes a corrugated construction on the annular sidewall.

Abstract: A drill bit for placement on a trenchless drill, the drill bit having a substantially rectangular construction, opposed side edges, a front end edge angularly related to the side edges, and a back end edge opposite the front end edge, opposed faces, with the edges having holes located therein and a cutting tooth press punched into each of the holes to form interference fits between the cutting teeth and the drill bit, the drill bit further having mechanism for attachment of the drill bit to the trenchless drill.