Impact of the typical errors in geotechnical core logging for geomechanical design in large caving mines

Authors: Russo, A; Montiel, E; Hormazabal, E

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DOI https://doi.org/10.36487/ACG_repo/2205_92

Cite As:
Russo, A, Montiel, E & Hormazabal, E 2022, 'Impact of the typical errors in geotechnical core logging for geomechanical design in large caving mines', in Y Potvin (ed.), Caving 2022: Proceedings of the Fifth International Conference on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 1319-1334, https://doi.org/10.36487/ACG_repo/2205_92

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Abstract:
Rock mass classification systems are widely used by geologists and geotechnical engineers for the classification, empirical design, and numerical modelling, especially during the first stages of a mining project, such as for Scoping and Pre-Feasibility studies. The most used systems in the mining industry are represented by Laubscher rock mass rating, Bieniawski rock mass rating, Barton Q, Laubscher and Jakubec in situ rock mass rating system, and Hoek–Brown geological strength index, consisting of empirical methods that characterise, in a simple and fast way, the rock mass quality while offering engineering applications to the geotechnical design, such as ground support design, pillar strength estimation, fragmentation, rock mass strength, caveability, among others. The authors have been involved in all the engineering stages of numerous large mining projects, from the scoping to the construction, passing through due diligence and peer review. When reviewing the geotechnical database of these projects, common and frequent errors seem to repeat, related to the collection of the basic geotechnical parameters. The most frequent errors are associated to a mistaken distinction among natural and mechanical discontinuities, erroneous joint counts and consequently FF/m calculation and a wrong assessment of the rock quality designation. Other typical errors have been detected in the assessment of the joint condition, most of them referred to the characterisation of the joint alteration (Ja) Barton parameter. The aim of this paper is to show the impact of the geotechnical errors and mistakes over the geomechanical design, quantifying the variation in terms of rock mass strength, caveability, pillar strength, Factor of Safety, etc., that will produce a negative impact on both the capex, opex and high risk for a mining project and/or operation.

Keywords: geotechnical core logging, geotechnical error, rock mass characterisation, geomechanical design

References:
Barton, N, Lien, R & Lunde, J 1974, ‘Engineering classification of rock masses for the design of tunnel support’, Rock Mechanics, vol. 6, pp. 189–236.
Bieniawski, ZT 1974, ‘Estimating the strength of rock materials’, Journal of The South African Institute of Mining and Metallurgy, vol. 74, no. 8, pp. 312–320,
Bieniawski, ZT 1989, Engineering Rock Mass Classifications: A Complete Manual for Engineers and Geologists in Mining, Civil, and Petroleum Engineering, Wiley-Interscience Publication - John Wiley & Sons.
Carranza-Torres, C & Fairhurst, C 2000, ‘Application of the convergence-confinement method of tunnel design to rock masses that satisfy the Hoek-Brown failure criterion’, Tunnelling and Underground Space Technology, vol. 15, no. 2, pp. 187–213.
Deere, DU & Deere, DW 1988, ‘The rock quality designation (RQD) in practice’, in L Kirkaldie (ed), Rock Classification Systems for Engineering Purposes, ASTM STP 984, ASTM International, West Conshohocken.
Deere, DU, Hendron, AJ, Patton, FD & Cording, EJ 1967, ‘Design of surface and near surface construction in rock’, in C Fairhurst (ed), Proceedings of the 8th U.S. Symposium on Rock Mechanics–Failure and Breakage of Rock, American Institute of Mining, Metallurgical and Petroleum Engineers, Inc., New York, pp. 237–302.
Flores, G & Catalan, A 2019, ‘A transition from a large open pit into a novel “macroblock variant” block caving geometry at Chuquicamata mine, Codelco Chile’, Journal of Rock Mechanics and Geotechnical Engineering, vol. 11, no. 3, pp. 549–561.
Grimstad, E & Barton, N 1993, ‘Updating the Q-System for NMT’, in C Kompen, SL Opsahl & SL Berg (eds), Proceedings of the International Symposium on Sprayed Concrete - Modern Use of Wet Mix Sprayed Concrete for Underground Support, Norwegian Concrete Association, Oslo.
Hamdi, P, Stead, D & Elmo, D 2017, ‘A review of the application of numerical modelling in the prediction of depth of spalling damage around underground openings’, Proceedings of the 51st US Rock Mechanics/Geomechanics Symposium, vol. 4, American Rock Mechanics Association, Alexandria, pp. 2874–2882.
Hoek, E, Carranza-Torres, C, Diederichs, MS. & Corkum, B 2008, ‘Integration of geotechnical and structural design in tunnelling’. Proceedings of the University of Minnesota 56th Annual Geotechnical Engineering Conference, pp. 1–53.
Hoek, E & Marinos, PG 2009, ‘Tunnelling in overstressed rock’, in I Vrkljan (ed), Rock Engineering in Difficult Ground Conditions - Soft Rocks and Karst, Taylor and Francis Group, London, pp. 49–60.
Hoek, E & Brown, ET 2019, ‘The Hoek–Brown failure criterion and GSI – 2018 edition’, Journal of Rock Mechanics and Geotechnical Engineering, vol. 11, no. 3, pp. 445–463,
Hoek, E, Carter, TG & Diederichs, MS 2013, ‘Quantification of the geological strength index chart’, Proceedings of the 47th US Rock Mechanics/Geomechanics Symposium, vol. 3, American Rock Mechanics Association, Alexandria, ARMA 13-672,
pp. 1757–1764.
Hudson, JA & Priest, SD 1979, 'Discontinuities and rock mass geometry'. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts, vol. 16, no. 6, pp. 339–362,
ISRM 1978, ‘Suggested methods for the quantitative description of discontinuities in rock masses’, International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, vol. 15, pp. 319–368.
Laubscher, D 1990, ‘Geomechanics classification system for the rating of rock mass in mine design’, Journal of the South African Institute of Mining And Metallurgy, vol. 90, no. 10, pp. 257–273.
Laubscher, D & Jakubec, J 2001, ‘The MRMR rock mass classification for jointed rock masses’, in W Hustrulid & R Bullock (eds), Underground Mining Methods, Society for Mining, Metallurgy, and Exploration, Englewood, pp. 475–481.
Palmstrom, A 1982, ‘The volumetric joint count - a useful and simple measure of the degree of rock mass jointing’, Iv Congress International Association of Engineering Geology, vol. 2, no. 3, pp. 221–228.
Palmstrom, A 2001, ‘Measurement and characterizations of rock mass jointing’, in VM Sharma & KR Saxena (eds), In-Situ Characterization of Rocks, A.A. Balkema, Rotterdam, pp. 1–40.
Palmstrom, A 2005, ‘Measurements of and correlations between block size and rock quality designation (RQD)’, Tunnelling and Underground Space Technology, vol. 20, no. 4, pp. 362–377,
Russo, A & Hormazabal, E 2016, ‘A methodology to select valid results from Lab tests to estimate properties of intact rock with microdefects’, Proceedings of the 50th US Rock Mechanics/Geomechanics Symposium, vol. 4, American Rock Mechanics Association, Alexandria, pp. 2659–2663.
Russo, A & Herrera, C 2011, ‘Impacto de la estimación de las propiedades geotécnicas de la roca intacta en el diseño de fortificación, Proyecto Mina Chuquicamata Subterranea’, SIMIN 2011: XVII Simposium de Ingeniería en Minas.




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