Failure behavior of rock and steel slag cemented paste backfill composite structures under uniaxial compression: Effects of interface angle and steel slag content

Abstract

The stability of the “surrounding rock-backfill” composite system is crucial for the safety of mining stopes. This study systematically investigates the effects of steel slag (SS) content and interface angle on the strength and failure characteristics of rock and SS-cemented paste backfill composite specimens (RBCS) through uniaxial compression strength tests (UCS), acoustic emission systems (AE), and 3D digital image correlation monitoring technology (3D-DIC). The intrinsic mechanism by which SS content influences the strength of SS-CPB was revealed through an analysis of its hydration reaction degree and microstructural characteristics under varying SS content. Moreover, a theoretical strength model incorporating different interface angles was developed to explore the impact of interface inclination on failure modes and mechanical strength. The main conclusions are as follows: The incorporation of SS enhances the plastic characteristics of RBCS and reduces its brittleness, with the increase of SS content, the stress–strain curve of RBCS in the “staircase-like” stage becomes smoother; When the interface angle is 45°, the RBCS stress–strain curve exhibits a bimodal feature, and the failure mode changes from Y-shaped fractures to interface and axial splitting; The addition of SS results in a reduction of hydration products such as Ca(OH)₂ in the backfill cementing system and an increase in harmful pores, which weakens the bonding performance and strength of RBCS, and the SS content should not exceed 45%; As the interface angle increases, the strength of RBCS decreases, and the critical interface slip angle decreases first and then increases with the increase in the E_S/E_R ratio. This study provides technical references for the large-scale application of SS in mine backfill.

Keywords

steel slag-cemented paste backfill / interface angle / rock-backfill composite structures / failure mode

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Central South University