Characterisation of fibre-reinforced backfill/rock interface through direct shear tests

Abstract

This paper reports on the results of a laboratory investigation on the shear behaviour of the interface between granite rock and cemented paste backfill (CPB) reinforced with different amounts of fibre (F-CPB) and cured at room temperature for different lengths of time by performing direct shear tests. Moreover, various microstructural analysis techniques are also used to characterise the degree of cementation of the cemented matrix, as well as the microstructure of the interface. The results indicate that the shear properties and behaviour of the F-CPB/rock interface are a function of the fibre content (optimal fibre content) and reduce the contraction at the interface. It is also found that the optimal fibre content is a function of the curing time and applied normal stress. The shear strength envelopes indicate that the friction angle at the interface is larger in the sample that contains fibres, whereas fibre reinforcement reduces the interface adhesion. The results of this research will contribute to improvements in the design and stability assessments of fibre-reinforced cemented-backfill structures.