Abstract: The present invention is directed to an anchor assembly for installing a threaded mine-roof bolt under tension in a bore hole formed in underground passageways, mines, and the like. The anchor assembly includes a two compartment resin cartridge and a mechanical expansion unit. A support collar is threaded on the bolt to restrict axial movement of the mechanical expansion unit. The mechanical expansion unit includes a camming plug and an expansion shell. The expansion shell has a plurality of fingers extending upwardly from an annular collar. Spaces or slots are formed between adjacent fingers. Each of the plurality of fingers include a vertically extending rib for forming channels between the external surfaces of the fingers and the side walls of the bore hole to permit the free flow of resin. The side surfaces of the fingers adjacent the uppermost portion thereof are tapered so that substantially V-shaped notches are formed between adjacent fingers.