Authored by Daniel Villa, GEOVIA Industry Process Consultant Expert.
In Article 1 of this series, an international copper mining company wanted to find out if it would be possible to increase productivity and reduce operating costs at a new block-caving project by changing their original design to accommodate new, larger load-haul-dump (LHD) machines.
Using a parametric design tool from Dassault Systèmes, the company tested the effect of the larger LHDs on their original mine design in a number of key parameters, such as tunnel spacing and undercut and extraction level elevation. From there, as described in Article 2, they used Dassault Systèmes’ PCBC mine planning software and other tools to automatically analyse selected parametric designs and, for each design, to:
- generate new draw point distribution
- create draw columns, based on block model and grade distribution data, to suit each tunnel spacing
- run best of height draw (BHOD) simulations to estimate economic mineable reserve, and
- calculate the economic reserve and create a summary of average copper value, average economic value, and total tonnes extracted — with all physical and economic parameters mapped to, and captured in, the DOE.
After the company’s mine planner selected the favourite scenarios, based on economic results, it was time to use simulation to complete advanced geotechnical analyses.
Block Caving’s Geotechnical Challenges
Block caving requires a very large deposit, with sufficient height and footprint area, to be cost effective. It should also ideally include certain geotechnical characteristics, such as pre-existing rock fractures to speed fragmentation and enough rock mass strength to support extraction tunnels.
But those characteristics can be hard to assess, and there is always the risk that the deposit will simply be too solid to cave or that it will collapse unpredictably, making it difficult to extract the ore efficiently and also potentially hazardous for workers and equipment. In addition, mines do not want to design a block caving project that will lead to air gaps during cave propagation, which can cause dangerous air blasts.
Geomechanical Simulation
Geomechanical simulation can help mines understand factors such as:
- whether there is enough ground support for a block-caving project
- if a particular design will result in subsidence and a large crater on the surface, and
- how large the economic recovery might be.
The copper company was particularly concerned that, while it looked like they had a good formation of high-grade material within their proposed mine design, there may be problems with vertical cave propagation. Specifically, they feared that the formation may not be able to propagate fast enough to avoid air gaps, which would have a major effect on extraction level location and extraction strategy.
In order to better understand and calibrate cave-back stress and the potential for breakthrough, the company’s mine designer took the draw points identified in Dassault Systèmes’ PCBC mine planning software and sent them to our geotechnical simulation software, Abaqus.
From there, Abaqus ran a series of scenario simulations using a variety of inputs — including swell factor, friction angle, cohesion, strain value, and principal stresses — to reveal the answer to what could be a billion-dollar question: where the limit between broken and solid material should be located.
Results
For the copper company, the geotechnical simulations revealed that the extraction strategy they had been pursuing was wrong. It was too aggressive and would generate a large air gap very quickly.
As a result, the designer changed the strategy to pull material more slowly and allow enough time for the cave to mature and propagate — a change that would have a major impact on NPV.
This graphic shows the difference in NPV between two possible extraction strategies:
“Investigating Economic and Risk Metrics Using Design of Experiments in Fully Coupled Caving Geomechanics Simulation” (Caving 2022. S. Arndt, D. Villa, F. Khodayari, B. Ndlovu.)
What comes next
The final article in this series looks at how the real-life copper company evaluated thousands of production scenarios before arriving at a design that would create a smaller, but significantly more productive underground mine than its original mine design.
Community is a place for GEOVIA users – from beginners to experts and everyone in between – to get answers to your questions, learn from each other, and network. Join our community to know more:
GEOVIA User Community – Read about industry topics from GEOVIA experts, be the first to know about new product releases and product tips and tricks, and share information and questions with your peers. All industry professionals are welcome to learn, engage, discover and share knowledge to shape a sustainable future of mining.
New member? Create an account, it’s free! Learn more about this community HERE.
When mining companies seek to increase mine productivity, they turn to Dassault Systèmes for technology and services. It is home to world-renowned and award-winning mining solutions and to industry thought leaders who are pushing the boundaries of what’s possible in mining, through the GEOVIA brand. The largest global supplier of mining software, GEOVIA delivers comprehensive solutions in all major mining centers in more than 130 countries at over 4,000 sites.