Abstract

An improved expansion assembly for a mine roof bolt adapted for use in a 11/2" diameter bore hole with a 1" roof bolt. The expansion assembly has a plug with tapered surfaces, an expansion shell with leaves extending axially upwardly from a support ring into contact with the tapered surfaces of the plug and a support washer. The inner surface of the expansion leaves are spaced inwardly from the surface of the support ring. The expansion leaves have serrations on their outer surfaces such that the serrations are formed by the intersection of a planar surface perpendicular to the axis of the mine bolt and a frusto-conical surface. The end of the leaves on the expansion shell have vertical serrations parallel to the longitudinal axis of the leaf. The tapered plug has channels running longitudinally between the surfaces on the plug for facilitating use of the expansion assembly with resin. The improved expansion assembly may be utilized with or without resin bonding.