Abstract
The presence of discontinuities (cold, batch, flow, slick, slurry or water joints) within cemented paste backfill are known to have an impact on the stability of underhand stope exposures. Currently there is limited understanding of the mechanical properties of these internal discontinuities. A geomechanical testing program has been completed that measures the tension response of synthetic discontinuities that have been created in cemented paste backfill in the laboratory. Three-dimensional modelling has been completed to demonstrate the effect on stability from the presence of discontinuities within a CPB fill mass that create backfill beams. It has been shown that when a backfill beam height is greater than 70% of the span width, its presence is unlikely to cause instability issues. As such, it is advised that this value be considered as the minimum thickness of a continuous plug pour to minimise dilution.