Multi-scale quantitative study on cemented tailings and waste-rock backfill under different loading rates

Abstract

The development of metallic mineral resources generates a significant amount of solid waste, such as tailings and waste rock. Cemented tailings and waste-rock backfill (CTWB) is an effective method for managing and disposing of this mining waste. This study employs a macro-meso-micro testing method to investigate the effects of the waste rock grading index (WGI) and loading rate (LR) on the uniaxial compressive strength (UCS), pore structure, and micromorphology of CTWB materials. Pore structures were analyzed using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The particles (pores) and cracks analysis system (PCAS) software was used to quantitatively characterize the multi-scale micropores in the SEM images. The key findings indicate that the macroscopic results (UCS) of CTWB materials correspond to the microscopic results (pore structure and micromorphology). Changes in porosity largely depend on the conditions of waste rock grading index and loading rate. The inclusion of waste rock initially increases and then decreases the UCS, while porosity first decreases and then increases, with a critical waste rock grading index of 0.6. As the loading rate increases, UCS initially rises and then falls, while porosity gradually increases. Based on MIP and SEM results, at waste rock grading index 0.6, the most probable pore diameters, total pore area (TPA), pore number (PN), maximum pore area (MPA), and area probability distribution index (APDI) are minimized, while average pore form factor (APF) and fractal dimension of pore porosity distribution (FDPD) are maximized, indicating the most compact pore structure. At a loading rate of 12.0 mm/min, the most probable pore diameters, TPA, PN, MPA, APF, and APDI reach their maximum values, while FDPD reaches its minimum value. Finally, the mechanism of CTWB materials during compression is analyzed, based on the quantitative results of UCS and porosity. The research findings play a crucial role in ensuring the successful application of CTWB materials in deep metal mines.

Keywords

cemented backfill / waste rock / loading rate / multi-scale analysis / mercury intrusion porosimetry / pore structure / micromorphology

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