Insights from the Heap Leach Mining Solutions 2016 conference by Jorge Castillo, Manager, Geotechnical and Engineering.
The Heap Leach Mining Solutions 2016 conference held recently in Peru, presented an excellent opportunity to talk to many of the leaders in this sector.
During the conference, a diverse range of topics were discussed, including: seismic influence, geotechnical investigation and analyses, design of heap leach facilities, heap leach operations, mineralogy, process optimization and water balance.
Over the course of the three day event, the biggest topics of discussion focused on geotechnical engineering analyses and on the design of heap leach pads. My key takeaways were:
- The critical importance of site specific risk assessments. With the recent high visibility tailings storage facilities (TSF) failures and the potential for 1 or 2 TSF failures per year (globally), it was highly recommended that all new and existing projects (TSF and heap leach pads) include a site-specific risk assessment. This assessment should include elements associated with design, construction, operation and closure of heap leach facilities.
- The value of 3D stability analyses in valley-fill heap leach pads under both static and seismic stability analyses. The geometry of the failure mechanism, which includes topography relief of the valley, the shear strength interface of the liner system, and other mechanical properties means that the analysis provided by 3D stability modelling is vital to provide accurate results. Presentations demonstrated that, in some instances, 2D analyses can be unrealistic and may be over-conservative. A strong field and laboratory investigation program is vital in providing detailed geotechnical characterization of each component of a heap leach facility.
- Non-saturated soils and transient seepage analyses needs to be performed in heap leach pads with fine ore, as these pads can generate excess pore pressure when solution is applied (irrigation rate or injection) exceeding the ore hydraulic conductivity. Saturated zones (or near saturation) can impact the global physical stability of the heap leach pads (during operations and/or long term), in particular where projects are located in high seismic areas.
- Project specific ore dynamic properties should be used for heap leach pad dynamic stability analyses. Using existing published soils (sand and gravel) and rockfill curves for ore dynamic properties might induce an unrealistic seismic response of heap leach pads.
Ausenco has carried out, and successfully applied, the key aspects discussed above to our recent projects.
For more information, contact the author Jorge Castillo (Jorge.Castillo@ausenco.com) or visit http://www.ausenco.com/heap-leach-facility-design .
Additionally, Scott Elfen our Global Practice Lead - Environment & Sustainability (Scott.Elfen@ausenco.com) is available to discuss how we can assist you.