Consolidation evaluation of tailings slurry considering rock mass drainage properties in underground stopes

Authors: Ma, Q; Liu, G; Yang, X; Guo, L

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DOI https://doi.org/10.36487/ACG_repo/2655_17

Cite As:
Ma, Q, Liu, G, Yang, X & Guo, L 2026, 'Consolidation evaluation of tailings slurry considering rock mass drainage properties in underground stopes', in AB Fourie, M Horta, M Oliveira & S Wilson (eds), Paste 2026: Proceedings of the 28th International Conference on Paste, Thickened and Filtered Tailings, Australian Centre for Geomechanics, Perth, pp. 1-12, https://doi.org/10.36487/ACG_repo/2655_17

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Abstract:
In open stoping with subsequent backfill mining, the backfilled tailings slurry in one stope is typically surrounded by the rock mass in adjacent stopes. The rock mass generally contains geological faults and joints that can serve as drainage pathways for water seepage within the backfill slurry during its consolidation process. However, the effects from the adjacent rock mass were traditionally simplified to be a totally impermeable or permeable boundary in previous studies. In this paper, numerical modellings with FLAC3D were firstly conducted to investigate the influences of hydro-geotechnical properties of surrounding rock mass on consolidation process of the uncemented tailings slurry in a vertical stope. Results show that the porewater pressure (PWP) and effective stresses of the slurry confined by rock mass are consistently higher than those obtained by assuming fully permeable boundaries, but obviously lower than those derived from impermeable boundary assumptions. A five-fold difference in peak PWP and effective stresses occurs when the rock mass hydraulic conductivity varies within common ranges from 10-8 m/s to 10-5 m/s. It is reasonable to simply understand the rock mass to be an impermeable boundary with a hydraulic conductivity lower than 10-8 m/s and a permeable boundary when it has a high hydraulic conductivity larger than 10-5 m/s. Additionally, a higher porosity and lower initial saturation of the adjacent rock mass promote both PWP dissipation and effective stresses development in backfill slurry, but their influences are relatively less pronounced compared to hydraulic conductivity of rock mass. Besides, the numerically simulated PWP and effective vertical stress were validated by comparisons with analytical results of Gibson model and modified Marston model, respectively. The findings are expected to provide valuable insights into the consolidation behaviour of tailings backfill slurry under field conditions and contribute reliable method for barricade design.

Keywords: tailings slurry, consolidation, porewater pressure, effective stress, rock mass drainage, FLAC3D

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