Cemented paste backfill failure envelope at low confining stress

A popular method to determine backfill strength for sidewall exposure assumes that the cohesive bond strength is equal to one-half the Unconfined Compressive Strength (cb = ½ UCS). A new laboratory study uses direct shear, UCS, and novel tensile strength test results to show that this strength assumption is not valid for the tested CPB (and quite possibly many other CPBs). The implications of this finding in the context of strength for exposed backfill sidewalls is investigated using generalized design examples.