Many hydraulic backfills are deposited at low density and provide less than optimum support strength to stope walls. This laboratory study shows that fill strength can be considerably increased. Placement methods used to increase the fill strength were the head, vibratory, cementation, double-placed, and combinations of these methods. An experimental facility was designed to study the placement methods and resultant strengths of the fills. Physical property tests made on the fills included laboratory penetration and vane shear plus several supplementary tests, such as grain size distribution and relative density. Test results were compared with fills placed by conventional methods and to those results reported by other investigators. Compared with fills placed by conventional methods, the penetration modulus was increased by 4.3 Times when the uncemented-vibrated-head concept was used and 71 times when the cemented-vibrated-head-double-placed concept was used. Apparently, hydraulically fill strength can be substantially increased. Conceptual mining plans are also included on suggested ways of placing and using high-modulus backfills.