Experimental investigation on interface mechanical properties between cemented paste backfill and rock based on direct shear tests

The shear strength of the interface between cemented paste backfill(CPB) and rock is of practical importance in analysis of stress distribution in backfilled stope and mine operators to balance strength.This paper aims at investigating the interface shear strength behavior between CPB and rock.The tests are performed on real backfill and granite.The shear tests are conducted at three different constant normal stress levels on flat and smooth interfaces.All tests are carried out in a standard direct shear test apparatus for a range of curing ages of 7 to 28 days, and three different cement tailings ratios for the CPB.Both cohesion, friction angle, peak and residua strengths are determined.The results show that the shear strength parameters and behavior of the CPB-rock interface are time-dependent and significantly influenced by cement content and the normal load, the peak shear strength and residual shear strength of the CPB-rock interface increase linearly with the increase of normal stress; the peak shear strength increases significantly with the increase of cement content and curing age, but the residual shear strength is insensitive to the change of cement content and curing age; besides the mechanical parameters of CPB-rock interface and CPB can be fitted with a certain line.