TECHNICAL BACKING AND SPECIALISED PUBLICATIONS
Scientific development and analytical models presented at the leading global conferences and successfully implemented at major mining operations.
Our directors and specialists actively contribute to the evolution of global industry standards. Through a solid track record in applied research, the presentation of papers at the most prestigious international seminars and the development of our own analytical methodologies — such as the McPhail model for predicting beach profiles — we back each of our projects with applied science that optimises safety and stability in mining.
A. High-density tailings
Sustainable Tailings Management (2008)
- Authors: McPhail, G and George, T.
- Event / Publication: Environmental Management in Mining Conference, 8-10 December 2008, Perth, Australia.
- Technical Summary: A strategic paper aimed at transforming tailings management from a reactive approach to a proactive, integrated sustainability methodology. The paper introduces a quantitative evaluation framework for site and technology selection, structured around the four pillars of Corporate Social Responsibility (CSR): economic viability, environmental stability, social impact and corporate governance. Through a comparative analysis of various transport and deposition alternatives, the study demonstrates the superior performance of high-density (thickened tailings) systems in reducing long-term liabilities, promoting an objective, auditable decision-making process aligned with international mining sustainability standards.
Implications of different tailings disposal options on future rehabilitation (2006)
- Authors: McPhail, G.
- Event / Publication: Mine Tailings, 26-27 February 2006, Brisbane, Australia.
- Technical Summary: A high-level technical and strategic paper for corporate decision-makers that analyses the impact of different tailings deposition technologies on actual rehabilitation costs and long-term financial liability. The paper introduces a paradigm shift in the economic evaluation of projects (trade-off studies), proposing to replace traditional discounted cash flow analyses (Net Present Cost) with direct comparisons of total cost at present value, avoiding the underestimation of decommissioning costs. Based on criteria of geomorphological stability and control of water erosion, the study shows that adopting high-density technologies makes it possible to configure free-draining surface landforms (shedding landforms) with optimum slopes of 1:20 or flatter. This configuration eliminates dependence on critical systems such as decant towers and complex underdrainage infrastructure, enabling progressive remediation schemes and drastically reducing the risk of financial surprises on mining companies’ balance sheets.
Probabilistic dam break assessment and flow slide analysis for tailings storage facilities (2015)
- Authors: McPhail, G.
- Event / Publication: Proceedings of the 3rd International seminar on tailings management, 19-21 August 2015, Santiago, Chile.
- Technical Summary: A highly specialised technical and strategic paper that introduces a predictive and preventive framework for the probabilistic assessment of dam breaks and flow slide analysis in tailings storage facilities. Based on the analysis of historical catastrophic collapses, the study shows that failures originate from complex chains of concurrent events that trigger static liquefaction of the material. The paper develops a stochastic numerical model that integrates fault and event tree analysis with probability density functions to model the variables of greatest uncertainty: discharge rate and volume over time, breach width, rheology of the mobilised tailings and lateral spreading distance. This semi-quantitative methodology makes it possible to accurately determine the risk of impact and flow height over critical infrastructure, serving as a design tool for implementing protective works and operating protocols capable of breaking the chain of failures and preventing socio-environmental disasters.
Environmental Aspects of Uranium Projects (2012)
- Authors: McPhail, G.
- Event / Publication: May 26-June 2012, Burswood Convention Centre, Perth, Australia.
- Technical Summary: A specialised strategic paper that analyses the regulatory challenges, public perception and engineering criteria required to mitigate long-term environmental liabilities in uranium projects. Drawing on the author’s experience at highly complex global operations, the paper examines the specific risks associated with toxicity, the longevity of daughter products and gas emissions in critical components such as waste rock dumps, heap leach pads, tailings storage facilities and haul routes. The study looks in depth at the methodological shift from conventional concentration-based control to management based on exposure dose limits, and sets out rigorous guidelines for establishing environmental baselines, continuous community monitoring and robust mitigation plans for the post-closure phase.
Waste rock dump decommissioning at mines in northern Western Australia (2003)
- Authors: McPhail, G.
- Event / Publication: Goldfields Environmental Conference 2003, Kalgoorlie, Australia.
- Technical Summary: A specialised technical paper focused on the engineering challenges of the final closure of large-scale waste rock dumps (up to 400 m high) exposed to extreme weather events such as tropical cyclones. The paper comprehensively analyses the concurrent phenomena of physical instability — characterised by high rates of water erosion and large consolidation settlements — and the chemical risks arising from the mobilisation of hydroxides and contaminating inorganic salts through infiltration. It describes the development and evaluation of decommissioning and closure alternatives, weighted against criteria of constructability, effectiveness and cost-reliability, with particular emphasis on the design of covers and advanced systems for the management and control of torrential runoff.
Osborne High Density Discharge: An Update from 2004 (2007)
- Authors: McPhail, G. and Brent, C.
- Event / Publication: Proceedings 10th International Seminar on Paste and Thickened Tailings (Paste 2007), R.J. Jewell and A.B. Fourie (eds), 13-15 March 2007, Perth, Australia, Australian Centre for Geomechanics, pp. 339-350.
- Technical Summary: A full-scale operational follow-up that confirms the long-term success of the thickened tailings system implemented at Osborne Mine. The paper details the transition from conventional deposition (65% solids content) to high-density discharge (75% solids) using the innovative advancing cone methodology. It presents the results of the field geotechnical investigation campaigns — which included piezocone penetration tests (CPTu) and the calibration of stability and seepage models — confirming step-change reductions in water losses and in capital costs (CAPEX) for dam wall raising. It also analyses how the final geometry of the facility, configured as a free-draining dome with no ponding, optimises closure potential in the face of projected increases in mine life.
Development and Implementation of Thickened Tailings Discharge at Osborne Mine, Queensland, Australia (2004)
- Authors: McPhail, G., Noble, A., Papageorgiou, G. and Wilkinson, D.
- Event / Publication: Proceedings 7th International Seminar on Paste and Thickened Tailings (Paste 2004), 31 March – 2 April 2004, Cape Town, South Africa.
- Technical Summary: A technical and engineering case study on the design, transition and field implementation of a thickened tailings discharge system at the Osborne Mine underground copper–gold operation, located in a highly arid region of Australia. The paper details how adopting this technology not only met the initial objectives of maximising water efficiency and reducing dam wall raising costs, but also comprehensively reduced operating costs (OPEX) and optimised the available storage capacity. Through geotechnical and seepage assessments, the paper demonstrates a reduced risk of seepage into the ground and a substantial improvement in the closure potential and erosion control of the facility, providing the technical and economic basis for securing long-term regulatory approvals.
The high density thickened discharge tailings storage facility at Osborne Mine – a case history from inception to closure (2015)
- Authors: McPhail, G.
- Event / Publication: Proceedings of the 18th International Seminar on Paste and Thickened Tailings, 5-7 May 2015, Cairns, Australia.
- Technical Summary: A comprehensive case history documenting the complete life cycle — from conception and operation through to the final closure plans — of the emblematic high-density thickened tailings (HDTT) facility at Osborne Mine, after 20 years of operation and the processing of 29 Mt of ore. The paper sets out the operational challenges overcome over time, such as adapting the thickening system and beach characteristics to the introduction of complex ores from satellite deposits. It also evaluates the consolidated economic benefits of eliminating dam wall raises (CAPEX reduction) and of optimising OPEX through maximum water recovery at the plant. Finally, the paper details the advanced landform design criteria applied to configure a free-draining shedding mound with highly resilient erosion-control covers, ensuring the safe isolation of the tailings over a predictive horizon of 500 years and compliance with strict environmental guidelines for the surrounding area.
Simulation of the meandering flow path of a beaching slurry using a random walk technique (2015)
- Authors: McPhail, G.
- Event / Publication: Proceedings of the 18th International Seminar on Paste and Thickened Tailings, 5-7 May 2015, Cairns, Australia, pp. 469-478.
- Technical Summary: A technical and scientific paper that introduces an advanced mathematical method for optimising the geometry and maximising the slope of deposition beaches in conventional and thickened tailings storage facilities. The study describes the physical basis for increasing the beach angle by splitting the total flow into multiple simultaneous discharges of smaller volume. Through the innovative application of the random walk technique, the paper stochastically models the meandering trajectories of surface slurry flows, making it possible to determine the optimum number of discharge pipes and the minimum spacing between them to prevent recombination downslope. The predictive simulations were successfully validated against full-scale operational behaviour at multiple international mine sites.
Important Considerations in the Testing of High Density Tailings for Beach Profile Prediction (2012)
- Authors: McPhail, G., Becerra, M. and Barrera, S.
- Event / Publication: Proceedings 15th International Seminar on Paste and Thickened Tailings (Paste 2012), R.J. Jewell and A.B. Fourie (eds), 16-19 April 2012, Sun City, South Africa, Australian Centre for Geomechanics, Perth, pp. 93-102.
- Technical Summary: A leading technical and consulting paper that analyses the operational and chemical variables affecting the reliability of rheological tests and beach profile predictions in high-density tailings. The study quantitatively demonstrates that factors such as pH, flocculant type and dosage, the degree of shear thinning and density stratification of sands on the beach can alter yield stress by between 30% and 300%. The paper sets out the scale limitations of traditional laboratory tests and proposes a rigorous rheological testing protocol designed to capture the variability of slurry chemistry, concluding that sensitivity analyses are essential and that profiles should be presented using probabilistic approaches with confidence bands to mitigate design risks on greenfield projects and active operations.
Discussion on the influence of mineralogy on the rheology of tailings slurries (2013)
- Authors: McPhail, G.
- Event / Publication: Proceedings First International Seminar on Tailings Management, 28-30 August 2013, Santiago, Chile.
- Technical Summary: A specialised strategic paper that analyses the critical impact of complex mineralogy — specifically the presence of active clay groups (such as montmorillonite and smectite) — on the yield stress and rheological behaviour of tailings. The study shows how these clays, released during the fine grinding of hard-rock ores, alter the electrochemical charge balance of the slurry, inducing extreme variations in viscosity and compromising the efficiency of thickeners, pumping systems and the predictability of the beach profile. Based on experience accumulated on more than 15 major projects in Chile, Australia and South Africa, the paper proposes integrated management guidelines to mitigate operational risk, such as ore blending or batch processing integrated into the mine plan.
Observations of tailings flow and application of the McPhail beach profile model to oil sands and metal mine tailings (2013)
- Authors: Charlebois, L.E., McPhail, G.I., Revington, A., and van Zyl, D.
- Event / Publication: Proceedings Tailings and Mine Waste 2013, 3-5 November 2013, Banff, Calgary, Canada.
Evaluation of the Behaviour of High Density Tailings Deposition – CODELCO Pilot Plant (2012)
- Authors: Engels, J., McPhail, G., Jammett, R., and Pavissich, C.
- Event / Publication: Proceedings 15th International Seminar on Paste and Thickened Tailings (Paste 2012), R.J. Jewell and A.B. Fourie (eds), 16-19 April 2012, Sun City, South Africa, Australian Centre for Geomechanics, Perth, pp. 197-212.
Prediction of the beaching characteristics of hydraulically placed tailings (1995)
- Authors: McPhail, G.
- Event / Publication: PhD Dissertation submitted to the University of the Witwatersrand, Johannesburg, South Africa.
Thickening and deposition trials: laboratory through to industrial scale – Minera Esperanza (2014)
- Authors: Gaete, S., Bello, F., Engels, J. and McPhail, G.
- Event / Publication: Proceedings 17th International Seminar on Paste and Thickened Tailings, 8-12 June 2014, Vancouver, Canada, pp. 381-391.
Using small scale flumes to determine rheology at low shear rates (2014)
- Authors: McPhail, G.
- Event / Publication: Proceedings Second International Seminar on Tailings Management, 20-22 August 2014, Antofagasta, Chile.
Application of fluidised bed column testing to the assessment of beaching and segregation characteristics of mine tailings (2016)
- Authors: McPhail, G., Engels, J. and Ugaz, R.
- Event / Publication: Proceedings of the 19th International Seminar on Paste and Thickened Tailings, 5-8 July 2016, Santiago, Chile.
- Technical Summary: A technical paper introducing a disruptive laboratory method based on fluidised bed column testing to assess the segregation and evolving rheology of mine tailings on deposition beaches. Built on the principle that energy is a scalar quantity, the model uses gravity in a vertical conduit to simulate the loss of stream power caused by frictional effects and viscous forces in laminar flows. The methodology allows changes in solids content, rheology and particle size distribution along the beach profile to be correlated in a controlled and economical way. The data obtained from the column feed directly into the stream power and entropy predictive model, providing a high-precision tool for the geometric design of storage facilities, particularly advantageous on new (greenfield) projects where no prior operational infrastructure is available for field sampling.
Beach Profile Modeling at Centinela Mine, Chile (2017)
- Authors: McPhail, G., Bello, F. and Engels, J.
- Event / Publication: 4th International Seminar on Tailings Management, 12-14 July 2017, Santiago, Chile.
- Technical Summary: Description of the development, implementation and calibration of an optimised spigot distribution and discharge system at Minera Centinela, designed to produce a steeper beach profile. The paper details the technical scale-up process from pilot, semi-industrial and industrial trials — including large-scale tests with 20 independent simultaneous discharges — consolidating the operational transition to a system that currently processes more than 90,000 tonnes per day through the calibration of rheological parameters and laboratory estimates.
Prediction of the Beach Profile of High Density Thickened Tailings from Rheological and Small Scale Trial Deposition Data (2008)
- Authors: McPhail, G.
- Event / Publication: Proceedings 11th International Seminar on Paste and Thickened Tailings (Paste08), A.B. Fourie, R.J. Jewell, P. Slatter and A. Paterson (eds), 5-9 May 2008, Kasane, Botswana, Australian Centre for Geomechanics, Perth, pp. 179-188.
- Technical Summary: A technical paper that validates the extension and versatility of the stream power and entropy methodology for predicting beach profiles in high-density tailings storage facilities. The study comparatively analyses the use of small-scale experimental flume tests and pilot deposition trials as operational tools to derive shear stress versus shear rate rheograms. The paper examines the scale factors of both techniques, concluding that the representative integration of these laboratory tests with field design variables — such as pipe diameter, flow rate, actual slurry density and beach length — makes it possible to simulate the geometric behaviour and deposition angles at full scale with a high degree of reliability.
Beaching angles and evolution of stack geometry for thickened tailings. A review (2011)
- Authors: Simms, P., Williams, M.P.A., Fitton, T. and McPhail, G.
- Event / Publication: Proceedings 14th International Seminar on Paste and Thickened Tailings (Paste2011), R.J. Jewell and A.B. Fourie (eds), 5-7 April 2011, Perth, Australia, Australian Centre for Geomechanics, Perth, pp. 323-338.
- Technical Summary: A collaborative review paper that evaluates the state of the art and the reliability of global methods for predicting beach slopes and the geometric evolution of thickened tailings stacks. The paper addresses the problem of scale dependence, demonstrating why laboratory data should not be extrapolated directly to field conditions. The study comparatively analyses the three most successful mathematical models in the industry against real cases (such as the Bulyanhulu gold operation): the erosion–sedimentation equilibrium approach, lubrication theory for extended flows, and Dr McPhail’s energy dissipation model, the latter highlighted as the only methodology able to directly predict the transition to concave profiles and long-term channelised flows. The paper provides critical operating guidelines to mitigate geotechnical and geo-environmental risks through rheological control and the design of deposited layer thickness.
B. Landform restoration design
Erosion Control, How practical is it – really? (2006)
- Authors: McPhail, G.
- Event / Publication: Mine Closure Seminar 2006, Perth, Australia.
- Technical Summary: A critical analysis of the real effectiveness of traditional surface erosion control strategies at mine closure. Starting from the premise that erosion is an inevitable natural process which conventional methods (such as vegetation and rock armouring) only slow down, the study uses advanced numerical modelling to assess how mining companies can minimise their long-term legal liabilities. The paper quantitatively contrasts corrective solutions on existing structures (a brownfield scenario, through reprofiling and containment) with designs optimised from the outset (a greenfield scenario), providing practical guidelines and geometric design criteria which show that prevention at the planning stage is the most viable and cost-effective way to mitigate erosional impact.
Planning – Landform design concepts, Creating effective rock dumps and stockpile (2005)
- Authors: McPhail, G. and Wilkinson, D.
- Event / Publication: Creating effective rock dumps and stockpile, 26-27 May 2005, Perth, Australia.
- Technical Summary: A methodological guide to the strategic planning and geometric design of waste rock dumps and stockpiles under a plan-for-closure philosophy. The paper addresses the long-term liabilities and reputational risks associated with abandoning massive mining infrastructure, critically analysing the effectiveness of traditional industry slopes (such as the 20-degree standard). Based on an assessment of the unavoidable dynamics of the ground — such as structural settlement, changes in drainage patterns, surface erosion and leaching of contaminants — it establishes advanced landform design criteria and stresses the need for continuous interaction between the design, construction and field monitoring teams to ensure the physical and chemical stability of the asset after closure.
Comparison of the erosional performance of alternative slope geometries (2008)
- Authors: McPhail, G. and Rye, C.
- Event / Publication: Proceedings of the First International Seminar on the management of rock dumps, stockpiles and heap leach pads, 5-6 March 2008, Perth, Australia, pp. 277-288.
- Technical Summary: Quantitative evaluation and comparison of alternative slope geometries for waste rock dumps and heap leach pads. The study analyses how traditional designs based on successive berms often perform poorly in the long term owing to sediment clogging and overtopping of benches, leading to severe gully erosion. Using the SIBERIA landform evolution model, this paper provides design criteria and predictive guidelines that allow erosional stability to be integrated with overall geotechnical stability, mitigating in advance the high construction costs associated with slope remodelling at mine closure.
Optimising the erosional performance of store and release covers through appropriate landform design (2006)
- Authors: McPhail, G. and van Koersveld, A.
- Event / Publication: Proceedings of the First International Seminar on Mine Closure, 13-15 September 2006, Perth, Australia, pp. 549-558.
- Technical Summary: An engineering analysis focused on maximising the long-term erosional stability of store-and-release covers on tailings storage facilities and waste rock dumps. The study shows that the success of a cover depends not only on its thickness or percolation control, but on mitigating the formation of gullies through an optimised geometric landform design. Using advanced predictive modelling tools (SIBERIA software) combined with Digital Terrain Models (DTMs), the paper establishes practical guidelines to prevent exposure of the underlying materials during high-intensity weather events in arid climates, avoiding critical corrective remediation after site closure.