Strain localisation behaviour of cemented paste backfill

Abstract

Mine tailings are the most significant and most problematic sources of solid waste globally in the mining industry. The developing concept of sustainable mining warrants reusing mine wastes, particularly tailings. Cemented paste backfill (CPB) is a backfill method composed of dewatered tailings, a cementitious binder, and processed mine water. CPB reuses tailings in underground mine excavations, and as such, reduces the amount of surface-disposed tailings, mitigates the potential environmental impacts, and assists waste management. In this study, the strain localisation behaviour of a South Australian copper-gold underground mine CPB system was evaluated through a comprehensive experimental programme. Understanding the strain localisation behaviour helps evaluate CPB damage evolution and failure mechanism under real-life loading regimes. The three-dimensional digital image correlation (DIC) technique was used to measure the full-field of strain development on the surface of CPB samples during unconfined compressive strength (UCS) tests. With the use of several virtual extensometers, the axial and lateral strains of CPB samples, with and without strain localisation, in both pre-peak and post-peak regimes are characterised. Overall, the DIC technique provides more accurate stress-strain relations of CPB samples than conventional external measurement devices. The DIC test results indicate that strain localisation of CPB samples initiates in the pre-peak regime at around 80% of the UCS. The greater the binder content and the longer the curing time, the higher the axial stress level required to initiate localisation to the UCS, thus emulating the failure mechanism of quasi-brittle materials -rock and concrete. Finally, with the increase of curing time, the difference between strain values at the localised and non-localised zones became less significant in the pre-peak regime and more pronounced in the post-peak regime.

Mitigating Risks in Coal Mining: Simulation-Based Strategy for Oxidation Zone Control Using Inorganic Paste Backfill at the Working Face Corners

“…This study holds immense significance in mitigating air leakage in the working face and ensuring safe mining operations. While the existing literature has extensively explored inorganic paste filling materials [15][16][17][18][19][20][21][22], this article introduces an innovative approach by using mountain sand as the filling aggregate and fly ash as the filling auxiliary material, resulting in a novel mountain sand-based paste filling material. This novel material demonstrates superior self-supporting properties, a quick setting time, and the ability to fully expand and reach the ceiling, as compared to other inorganic paste filling materials.…”

“…Liu Yong [19] conducted experiments on high-sand filling materials, using water, cement, fly ash, and wind-blown sand as inorganic filling aggregates, and determined the optimal concentration ratio suitable for water-preserving mining, significantly impacting water-preserving mining practices in western mining areas. Zhao Xuefei [20] utilized various fine-tail grains of sand as filling aggregates, examining the filling performance of cemented paste materials under different aggregates and additives, and found that substituting cement with high-alumina clay resulted in minimal changes in the compressive strength of the filling body while gradually enhancing stability in later stages. Zheng Juanrong [21] and collaborators introduced different types of early-strength agents to tailings cemented paste filling materials and discovered that Na 2 SO 4 and NaOH early-strength agents had superior effects.…”