Hydraulic fracturing as a novel technique for strength evaluation of cemented paste backfill: influence of injection flow rate on fracture initiation pressure

Authors: Frimpong, J; Pandey, R

Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2655_10

Cite As:
Frimpong, J & Pandey, R 2026, 'Hydraulic fracturing as a novel technique for strength evaluation of cemented paste backfill: influence of injection flow rate on fracture initiation pressure', 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. 1-13, https://doi.org/10.36487/ACG_repo/2655_10

Download citation as:   ris   bibtex   endnote   text   Zotero


Abstract:
Cemented paste backfill (CPB) is a critical ground control material in underground mining to provide support and stability to mined-out voids, and accurate strength assessment is essential for ensuring long-term stability and safety. Conventional strength evaluation methods, such as uniaxial compressive strength tests on surface-cured specimens, often fail to represent actual in situ conditions, leading to unreliable strength estimates. To overcome this limitation, a new laboratory technique based on hydraulic fracturing has been developed to directly evaluate CPB strength under in situ conditions. The method determines the fracture initiation pressure (FIP), the maximum pressure at which the backfill first fractures, which has been verified as a reliable indicator of CPB strength. This study focuses on investigating the role of injection flow rate in hydraulic fracturing tests as part of validating the technique. Cylindrical CPB samples were fractured using AW32 hydraulic oil at controlled flow rates ranging from 1 to 50 ml/min. Results show that flow rate influences fracture initiation at lower rates (1–8 ml/min). At these low rates, gradual fluid delivery causes slower pressurisation, increased fluid leak-off, and delayed fracture onset, resulting in reduced FIP values. As flow rate increases, FIP rises, reflecting more efficient pressurisation and reduced leak-off. However, beyond 8 ml/min, the influence of flow rate diminishes, and the inherent variability in sample strength becomes more significant than the variations in FIP caused by changes in flow rate. The findings highlight that flow rate is a critical parameter to consider when applying hydraulic fracturing for CPB testing. Practically, this study establishes a baseline recommendation: low flow rates are unsuitable for strength estimation. To obtain the most representative FIP-based strength index, higher injection flow rate should be used, where rate effects diminish and variability in FIP is dominated by material properties. These outcomes provide a strong foundation for advancing hydraulic fracturing as a reliable method for CPB strength assessment.

Keywords: cemented paste backfill, hydraulic fracturing, fracture initiation pressure, injection flow rate, strength assessment, ground control

References:
Aref, K 1988, A Study of the Geotechnical Characteristics and Liquefaction Potential of Paste Backfill, PhD thesis, McGill University, Montreal.
Arzuaga-Garcia, I & Einstein, H 2020, ‘Experimental study of fluid penetration and opening geometry during hydraulic fracturing’, Engineering Fracture Mechanics, vol. 230, p. 106986.
ASTM International 2017, Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens (ASTM C496/C496M17), ASTM International, West Conshohocken.
ASTM International 2023, Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens (ASTM C39/C39M21), ASTM International, West Conshohocken.
Been, K, Brown, ET & Hepworth, N 2002, ‘Liquefaction potential of paste fill at Neves Corvo mine, Portugal’, Transactions of the Institution of Mining and Metallurgy Section A – Mining Technology, vol. 111, pp. A47–A58.
Chen, G, Ye, Y, Yao, N, Fu, F, Hu, N & Zhang, Z 2022, ‘Deformation failure and acoustic emission characteristics of continuous graded waste rock cemented backfill under uniaxial compression’, Environmental Science and Pollution Research, vol. 29, no. 53, pp. 80109–80122, 
Chong, KP & Kuruppu, MD 1984, ‘New specimen for fracturetoughness determination for rock and other materials’, International Journal of Fracture, vol. 26, no. 2, pp. R59–R62, 
Ercikdi, B, Yılmaz, T & Külekci, G 2014, ‘Strength and ultrasonic properties of cemented paste backfill’, Ultrasonics, vol. 54, no. 1, pp. 195–204.
Fallahzadeh, SH, Hossain, MM, James Cornwell, A & Rasouli, V 2017, ‘Near wellbore hydraulic fracture propagation from perforations in tight rocks: the roles of fracturing fluid viscosity and injection rate’, Energies, vol. 10, no. 3, p. 359.
Frimpong, J & Pandey, R 2025, ‘Novel hydraulic measurement technique to enable reliable strength evaluation of cemented paste backfill in underground mines’, Proceedings of the 59th US Rock Mechanics/Geomechanics Symposium, American Rock Mechanics Association, Alexandria.
Frimpong, JA, Shabab, BA, Pandey, R, Chatterjee, S, Walton, G & Brand, AS 2025, ‘Fracture initiation pressure as a measure of cemented paste backfill strength’, Mining, Metallurgy & Exploration, vol. 42, no. 3,
pp. 1305–1323, 
Haimson, B & Fairhurst, C 1967, ‘Initiation and extension of hydraulic fractures in rocks’, Society of Petroleum Engineers Journal, vol. 7, no. 3, pp. 310–318.
Haimson, B & Fairhurst, C 1969, ‘Hydraulic fracturing in porouspermeable materials’, Journal of Petroleum Technology, vol. 21, no. 7, pp. 811–817.
Helinski, M 2007, Mechanics of Mine Backfill, PhD thesis, The University of Western Australia, Perth.
Hubbert, MK & Willis, DG 1957, ‘Mechanics of hydraulic fracturing’, Transactions of the American Institute of Mining and Metallurgical Engineers, vol. 210, no. 6, pp. 153–163.
Ito, T & Hayashi, K 1991, ‘Physical background to the breakdown pressure in hydraulic fracturing tectonic stress measurements’, International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, vol. 28, no. 4, pp. 285–293.
Johnson, JC, Seymour, JB, Martin, LA, Stepan, M & Akroosh, A 2015, ‘Strength and elastic properties of paste backfill at the Lucky Friday mine, Mullan, Idaho’, Proceedings of the 49th US Rock Mechanics/Geomechanics Symposium, American Rock Mechanics Association, Alexandria.
Kesimal, A, Yilmaz, E, Ercikdi, B, Alp, I & Deveci, H 2005, ‘Effect of properties of tailings and binder on the short and longterm strength and stability of cemented paste backfill’, Materials Letters, vol. 59, no. 28, pp. 3703–3709.
Klein, K & Simon, D 2006, ‘Effect of specimen composition on the strength development in cemented paste backfill’, Canadian Geotechnical Journal, vol. 43, no. 3, pp. 310–324.
Landriault, D 1995, ‘Paste backfill mix design for Canadian underground hard rock mining’, Proceedings of the 12th Mine Operators Conference, Canadian Institute of Mining, Westmount.
Le Roux, K, Bawden, WF & Grabinsky, MF 2002, ‘Comparison of the material properties of in situ and laboratory prepared cemented paste backfill’, Proceedings of the CIM Conference, Canadian Institute of Mining, Westmount.
Le Roux, K, Bawden, WF & Grabinsky, MF 2005, ‘Field properties of cemented paste backfill at the Golden Giant mine’, Transactions of the Institutions of Mining and Metallurgy Section A – Mining Technology, vol. 114, no. 2,
pp. A65–A80, 
Li, D, Liu, B, He, J, Li, X & Jian, M 2017, ‘Strength and transportability of cemented phosphogypsum paste backfilling slurry’, in A Wu & R Jewell (eds), Paste 2017: Proceedings of the 20th International Seminar on Paste and Thickened Tailings, University of Science and Technology Beijing, Beijing, pp. 328–336,
Mitchell, RJ 1991, ‘Sill mat evaluation using centrifuge models’, Mining Science and Technology, vol. 13, pp. 301–313.
Qiu, H, Zhang, F, Liu, L, Hou, D & Tu, B 2020, ‘Influencing factors on strength of waste rock tailing cemented backfill’, Geofluids, vol. 2020, article 8847623.
Sheshpari, M 2015, ‘A review of underground mine backfilling methods with emphasis on cemented paste backfill’, Electronic Journal of Geotechnical Engineering, vol. 20, no. 13, pp. 5183–5208.
Sivakugan, N, Veenstra, R & Naguleswaran, N 2015, ‘Underground mine backfilling in Australia using paste fills and hydraulic fills’, International Journal of Geosynthetics and Ground Engineering, vol. 1, article 1.
Stone, D 2021, ‘Paste quality control benchmarks’, MineFill 2020–2021: Proceedings of the 13th International Symposium on Mining with Backfill, pp. 35–43.
Ulven, OI & Sun, W 2018, ‘Capturing the twoway hydromechanical coupling effect on fluiddriven fracture in a dualgraph lattice beam model’, International Journal for Numerical and Analytical Methods in Geomechanics, vol. 42, no. 5, pp. 736–767.
Uwaifo, E 2016, Timedependent Initiation of Multiple Hydraulic Fractures in Rocks, PhD thesis, University of Pittsburgh, Pittsburgh.
Wang, F, Zheng, Q, Zhang, G, Wang, C, Cheng, FQ & Geng, L 2020, ‘Preparation and hydration mechanism of mine cemented paste backfill material for secondary smelting watergranulated nickel slag’, Journal of New Materials for Electrochemical Systems, vol. 23, no. 1, pp. 51–59, 
Whitney, JM & Nuismer, RJ 1974, ‘Stress fracture criteria for laminated composites containing stress concentrations’, Journal of Composite Materials, vol. 8, no. 3, pp. 253–265.
Xin, L 2021, ‘Mesoscale modeling of the influence of waste rock content on mechanical behaviour of cemented tailings backfill’, Construction and Building Materials, vol. 307, p. 124473.
Yilmaz, E 2010, Investigating the Hydrogeotechnical and Microstructural Properties of Cemented Paste Backfill Using the CUAPS Apparatus, PhD thesis, Université du Québec en AbitibiTémiscamingue, RouynNoranda.
Yin, S, Shao, Y, Wu, A, Wang, H, Liu, X & Wang, Y 2020, ‘A systematic review of paste technology in metal mines for cleaner production in China’, Journal of Cleaner Production, vol. 247, 119590, 
Yumlu, M & Guresci, M 2007, ‘Paste backfill bulkhead monitoring – a case study from Inmet’s Çayeli mine, Turkey’, Proceedings of the 9th International Symposium on Mining with Backfill.
Zhou, J, Zhang, L, Braun, A & Han, Z 2016, ‘Numerical modeling and investigation of fluiddriven fracture propagation in reservoirs based on a modified fluidmechanically coupled model in twodimensional particle flow code’, Energies, vol. 9, no. 9, p. 699.




© Copyright 2026, Australian Centre for Geomechanics (ACG), The University of Western Australia. All rights reserved.
View copyright/legal information
Please direct any queries or error reports to repository-acg@uwa.edu.au