Raiseboring in poor ground: consolidation and support methods

Authors: Smith, R; Rees, J; Behunin, J; Branham, J; Roselle, Z

DOI https://doi.org/10.36487/ACG_repo/2625_40

Cite As:
Smith, R, Rees, J, Behunin, J, Branham, J & Roselle, Z 2026, 'Raiseboring in poor ground: consolidation and support methods', in D Cumming-Potvin & J Wesseloo (eds), Ground Support 2026: Proceedings of the 11th International Conference on Ground Support in Mining, Australian Centre for Geomechanics, Perth, pp. 1-13, https://doi.org/10.36487/ACG_repo/2625_40

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Abstract:
At Rio Tinto Kennecott’s underground operation, ventilation raises and secondary egress escapeways are developed using raiseboring. Ground conditions in the underground mine are highly variable, ranging from good (Q > 10) to very poor (Q < 1.0). Following a raise failure in 2022 attributed to weak ground conditions, it became evident that vertical development would pose a challenge at Kennecott. In response to the increased risk of instability during raiseboring, site implemented strict controls including pre-support, lining, canning, controlled raiseboring rates and most critically, ground consolidation. Ground consolidation is achieved through grout rings, comprised of vertically drilled and grouted perimeter holes around a planned raisebore diameter. Primary, secondary, and where necessary, tertiary grout rings are strategically designed to target and consolidate weak rock masses and thick fault zones. Among the implemented controls, grout rings have proven to be highly effective in improving raise stability and stand-up time. Since adopting this methodology, 11 raises have been successfully developed in challenging ground without any stability issues. This paper presents an overview of the design methodology and execution strategies for grout rings. It outlines the overall approach to ensure successful raiseboring in challenging ground, and highlights key lessons learned to date.

Keywords: vertical development, raisebore, ground consolidation, grout rings

References:
Barton, N, Lien, R & Lunde, J 1974, ‘Engineering classification of rock masses for the design of tunnel support’, Rock Mechanics, vol. 6, no. 4, pp. 189–236,
Edelbro, C, Brummer, R, Pierce, M, Sandstrom, D & Sjoberg, J 2019, ‘Raiseboring in difficult rock conditions’, in J Hadjigeorgiou & M Hudyma (eds), Ground Support 2019: Proceedings of the Ninth International Symposium on Ground Support in Mining and Underground Construction, Australian Centre for Geomechanics, Perth, pp. 185–198,
ACG_rep/1925_11_Edelbro
McCracken, A & Stacey, TR 1989, ‘Geotechnical risk assessment for large-diameter raise-bore shafts’, Proceedings Shaft Engineering Conference, IMM, London, pp. 309–316.
Peck, W, Coombes, B & Lee, M 2011, ‘Fine-tuning raise bore stability assessments and risk’, 11th Underground Operators Conference, The Australasian Institute of Mining and Metallurgy, Melbourne, pp. 215–225.
Penney, AR, Stephenson, RM & Pascoe, MJ 2018, ‘Raisebore stability and risk assessment empirical database update’, AusRock 2018: The Fourth Australasian Ground Control in Mining Conference, The Australasian Institute of Mining and Metallurgy, Melbourne, pp. 435–445.
Scott, C, Evans, L & Lourence, P 2010, ‘Successful raiseboring in poor ground conditions, Kencana Mine, Indonesia’, in Second Australasian Ground Control in Mining Conference, AusRock, Sydney, pp. 255–260,
Scott, CG, Sidea, D & Masters, SJ 2023, ‘Ground support methods for vertical development’, in J Wesseloo (ed.), Ground Support 2023: Proceedings of the 10th International Conference on Ground Support in Mining, Australian Centre for Geomechanics, Perth, pp. 345–358,




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