Experimental investigation into the temperature effect on the shear behavior of the fiber-reinforced interface between rock and cemented paste backfill

Abstract

Considering the importance of the interaction between cemented paste backfill (CPB) and rock in determining the stability of underground CPB structures, a comprehensive understanding of the shear performance of the fiber-reinforced CPB/rock (FR-CPB/rock) interface is crucial to the CPB design. Despite some tentative exploration performed on the shear performance of the FR-CPB/rock interface, the coupled effects of temperature, binder type and fiber content on the interface behavior remain unrevealed. To fill this research gap, direct shear tests are carried out on FR-CPB/rock interface samples prepared with diverse binders and fiber contents (cured at 2℃, 20℃, and 35℃). The obtained results indicate that the shear strength of the FR-CPB/rock interface generally increases with temperature and curing time. Besides, compared with samples made with Portland cement type I (PCI), the usage of PCI and fly ash (PCI/FA (50/50)) negatively affect the shear strength of the FR-CPB/rock interface (owing to the low sensitivity of FA to temperature) but the adoption of PCI/slag (50/50) in CPB preparation can improve the shear strength (due to the alkaline activation of slag). Moreover, the addition of fiber can positively or negatively influence the shear strength of the interface, up to the fiber content. However, the frictional angle of the FR-CPB/rock interface increases with the fiber content, but the cohesion shows a descending tendency with the fiber content. The findings in this research serves the purpose of a comprehensive understanding of the shear behavior of the FR-CPB/rock interface and are meaningful in CPB design.