Yang, PY & Li, L 2017, 'Numerical and limit equilibrium stability analyses of cemented mine backfill upon vertical exposure', in M Hudyma & Y Potvin (eds), UMT 2017: Proceedings of the First International Conference on Underground Mining Technology
, Australian Centre for Geomechanics, Perth, pp. 399-408, https://doi.org/10.36487/ACG_rep/1710_31_Yang
In open stope mines, the cemented backfill must maintain self-standing in the primary stope during the extraction of an adjacent secondary stope. A limit equilibrium solution proposed by Mitchell et al. (1982) has been widely used since the 1980s to design the exposed cemented fill. This solution has been the object of several modifications over the years. Recently, the comparison between these solutions and numerical simulations indicated that the former are not fully representative of the exposed fill when its required cohesion is relatively large. In this paper, new numerical results show that the slip surface transitions from planar at low fill cohesion to spoon-shaped at larger cohesion. In the former case, the failure is controlled by shear stresses mobilised along the planar slip surface. This is very similar to the failure mode assumed in existing theoretical models. In the latter case, however, the failure is governed by both shear (near the base) and tensile (near the top) stresses, indicating a different failure mode. Based on these observations, a new analytical solution is proposed to evaluate the stability of side-exposed cemented fill. This solution is validated using complementary simulations and the results indicate that the two different approaches agree well for typical stope geometry and fill properties.
Keywords: exposed mine backfill, Mitchell et al. solution, limit equilibrium, numerical modelling
Askew, J, McCarthy, PL & Fitzgerald, DJ 1978, ‘Backﬁll research for pillar extraction at ZC/NBHC’, Proceedings of 12th Canadian Rock Mechanics Symposium on Mining with Backﬁll, Canadian Institute of Mining, Metallurgy and Petroleum, Westmount,
Bowles, JE 1984, Physical and Geotechnical Properties of Soils, 2nd edn, McGraw–Hill, New York.
Coulthard, MA 1999, ‘Applications of numerical modelling in underground mining and construction’, Geotechnical and Geological Engineering, vol. 17, no. 3–4, pp. 373–385.
Dirige, APE & De Souza, E 2000, ‘Centrifuge physical modelling of paste fill designs for improved cost performance’, Proceedings of the Millennium 2000 CIM Conference, Canadian Institute of Mining, Metallurgy and Petroleum, Westmount.
Dirige, APE & De Souza, E 2013, ‘Mechanics of failure of paste backfill face exposure during adjacent mining’, Proceedings of 23rd World Mining Congress, Canadian Institute of Mining, Metallurgy and Petroleum, Westmount.
Dirige, APE, McNearny, RL & Thompson, DS 2009, ‘The effect of stope inclination and wall rock roughness on back–fill free face stability’, in M Diederichs & G Grasselli (eds), Proceedings of the 3rd Canada–US Rock Mechanics Symposium: Rock Engineering in Difficult Conditions, (CD–ROM), Omnipress, Madison.
Emad, MZ, Mitri, H & Kelly, C 2014, ‘Effect of blast–induced vibrations on fill failure in vertical block mining with delayed backfill’, Canadian Geotechnical Journal, vol. 51, no. 9, pp. 975–983.
Falaknaz, N 2014, ‘Analysis of geomechanical behavior of two adjacent backfilled stopes based on two and three dimensional numerical simulations’, PhD thesis, Mineral Engineering, Polytechnique Montreal, Montreal.
Falaknaz, N, Aubertin, M & Li, L 2015, ‘On the stability of exposed backfill in mine stopes’, Proceedings of the 68th Canadian Geotechnical Conference, Canadian Geotechnical Society, Quebec.
Fall, M & Nasir, O 2010, ‘Mechanical behaviour of the interface between cemented tailings backfill and retaining structures under shear loads’, Geotechnical and Geological Engineering, vol. 28, no. 6, pp. 779–790.
Itasca Consulting Group, Inc., 2013, FLAC3D: Fast Lagrangian Analysis of Continua in 3 Dimensions; User’s Guide, Itasca Consulting Group, Inc., Minneapolis.
Jahanbakhshzadeh, A 2016, Analyse du Comportement Géomécanique des Remblais Miniers dans des Excavations Souterraines Inclines, PhD thesis, Mineral Engineering, Polytechnique Montreal, Montreal.
Koupouli, NJ, Belem, T, Rivard, P & Effenguet, H 2016, ‘Direct shear tests on cemented paste backfill–rock wall and cemented paste backfill–backfill interfaces’, Journal of Rock Mechanics and Geotechnical Engineering, vol. 8, pp. 472–479.
Li, L 2014, ‘Generalized solution for mining backfill design’, International Journal of Geomechanics, vol. 14, no. 3, pp. 04014006.
Li, L & Aubertin, M 2009, ‘Numerical investigation of the stress state in inclined backfilled stopes’, International Journal of Geomechanics, vol. 9, no. 2, pp. 52–62.
Li, L & Aubertin, M 2012, ‘A modified solution to assess the required strength of exposed backfill in mine stopes’, Canadian Geotechnical Journal, vol. 49, no. 8, pp. 994–1002.
Li, L & Aubertin, M 2014, ‘An improved method to assess the required strength of cemented backfill in underground stopes with an open face’, International Journal of Mining Science and Technology, vol. 24, no. 4, pp. 549–558.
Li, L, Aubertin, M, Simon, R, Bussière, B & Belem, T 2003, ‘Modelling arching effects in narrow backfilled stopes with FLAC’, Proceedings of the 3rd International Symposium on FLAC & FLAC 3D Numerical Modelling in Geomechnics, CRC Press, Boca Raton, pp. 211–219.
Liu, G, Li, L, Yang, X & Guo, L 2016, ‘Numerical modelling of the stability of cemented backfill with a vertical face exposed: a revisit to Mitchell’s physical model tests’, International Journal of Mining Science and Technology, vol. 26, no. 6, pp. 1135–1144.
McCarthy, DF 2002, Essentials of Soil Mechanics and Foundations: Basic Geotechnics, 6th edn, Prentice Hall, Englewood Cliffs.
Mitchell, RJ 1986, ‘Centrifuge model tests on backfill stability’, Canadian Geotechnical Journal, vol. 23, no. 3, pp. 341–345.
Mitchell, RJ, Olsen, RS & Smith, JD 1982, ‘Model studies on cemented tailings used in mine backfill’, Canadian Geotechnical Journal, vol. 19, no. 1, pp. 14–28.
Pierce, ME 2001, ‘Stability analysis of paste back fill exposes at Brunswick Mine’, Proceedings of the 2nd International FLAC Symposium, Swets & Zeitlinger Publishers, Lisse, pp. 147–156.
Yang, PY 2016, Investigation of the Geomechanical Behavior of Mine Backfill and its Interaction with Rock Walls and Barricades,
PhD thesis, Mineral Engineering, Polytechnique Montreal, Montreal.
Yang, PY, Li, L & Aubertin, M 2017b, ‘A new solution to assess the required strength of mine backfill with a vertical exposure’, International Journal of Geomechanics, vol. 17, no. 10.
Yang, PY, Li, L, Aubertin, M, Brochu–Baekelmans, M & Ouellet, S 2017a, ‘Stability analyses of waste rock barricades designed to retain paste backfill’, International Journal of Geomechanics, vol. 17, no. 3, pp. 04016079.
Zou, DH & Nadarajah, N 2006, ‘Optimizing backfill design for ground support and cost saving’, Proceedings of the 41st US Rock Mechanics Symposium: 50 Years of Rock Mechanics, American Rock Mechanics Association, Alexandria.