Effect of inclined interface angle on shear strength and deformation response of cemented paste backfill-rock under triaxial compression

Abstract Cemented backfilling has been widely used in underground mines worldwide. The stability of cemented backfill must be sufficient to maintain the subsequent stope. Investigation into the shear strength and deformation of cemented paste backfill-rock (CPB-rock) under triaxial compression is prominent important for mine operators and managers, while the knowledge of the effect of the interface between cemented paste backfill (CPB) and rock on the shear strength and deformation behavior is limited. The objective of this paper is to experimentally investigate the effect of interface angle on the triaxial deformation behavior and shear strength of the CPB-rock. Two interface angles (45° and 60°) and three cement contents (2.5, 5 and 7.5 wt%) were designed. All tests were carried out by a standard triaxial compression apparatus, and the confining stress levels were varied in a range corresponding to the in-situ horizontal pressures (σc ≤ 200 kPa). The results show that the interface angle plays a dominant role in the failure patterns of CPB-rock. Increasing the cement content improves the brittleness of CPB matrix, and increases the shear strength difference between CPB-rock and CPB. The failure pattern of CPB-rock changes from composite failure to slipping failure. At last, the bilinear peak strength envelope for CPB-rock specimens is proposed. The results are expected to quantify the effect of CPB-rock interface on stability of cemented backfill.