Modern approaches to infrastructure in mining

Tom Lynch, Senior Geotechnical Engineer, Cartledge Mining and Geotechnics

How earthworking smarter can lift efficiency and save costs

On a mine site, all roads lead to productivity, and it is the safety, stability and quality of these roads, along with other vital Infrastructure, that are major parts of a geotechnical engineer’s role.

It’s our responsibility to ensure the design of this infrastructure – haul roads, embankments, pads, levees, walls, dams and drains – contributes to optimal production.

Typically, when a main access road for a mine needs to be built, it would involve a civil-engineering approach – with the earthworks design specification mirroring processes, recommendations and actions of similar council or government projects.

Such a construction plan would include high-quality materials, tight placement specifications, and tight tolerances on the actual material properties. Mines would then source the desired material onsite, or purchase from a quarry at high costs. Then there’s usually the expense of external contractors and equipment to complete the job.  

It can unnecessarily become a costly, over-engineered project. A more modern approach can solve these challenges and reap cost benefits that make smart business sense.

Working with what you’ve got

There’s a solid argument for advising and encouraging mines to work with what is available – including materials and equipment.

Constant earthworks, blasting and general mining production, mean mine sites have substantial quantities of readily available material, suitable for building infrastructure. In most cases this material would otherwise be destined for the dump and, with waste disposal targets to be met, reducing the mine’s dump footprint is always a favourable option. Working with what is on hand also reduces the spend on buying and transporting in materials.

Such a shift in focus involves asking mines at an early stage in the planning process:

What material have you got? By the time you’re building this, where will you be digging in your mine, and what material will this unearth? And, what material would you like to use?

Knowing these answers enables geotechnical engineers to test selected material, and then build a specification to suit, rather than finding the material to suit the specification.

Lowering costs but not quality

For geotechnical engineers, the focus has traditionally been on recommending top-quality materials, as the build integrity and successful outcome is known.

When using on-hand materials, which save costs but could be sub-optimal, further considerations must be made around quality and durability, for example, erosion susceptibility, plasticity, or uneven compaction, and factored into the construction plan.

At the design stage, material must be tested to understand its properties, and then construction designed accordingly to mitigate any material challenges.

Allowing for deficiencies in a material susceptible to erosion, for example, would include making the road wider, so there’s a sacrificial layer that won’t impact structural integrity. And then as it erodes, it can be repaired periodically, with all of this factored into the design.

A key use case is a recent example of our work designing a 4.5km-long levee for a Bowen Basin open cut coal mine.

We engineered the project to use locally sourced material, which would have otherwise gone to a dump, ultimately saving dump space and enabling the mine to implement infrastructure at a lower cost. To accommodate material quality deficiencies, we designed the levee to be considerably larger than what it would have been if the best material was available. The right design was used, to match that material.

The mine site difference

The considerations for mine infrastructure design and construction can be quite different to a civil build for main roads or a municipality. Public works demand high standards, minimal upkeep and the least amount of disruption to the community.

On mine sites, while high standards must also be met, a major difference lies in having the capacity to live with a lower-quality material that needs more maintenance, as the impact on the public is out of the equation.

Maintenance on main roads disrupts traffic and people; while in mining, that’s not an issue. That’s not to say mining operations and production schedules are not considered – any forward-thinking construction plan must align with site targets and operations.

Driving better use of equipment on site

Using mine equipment to place and compact materials is another way to save costs and boost efficiencies. Mines usually have graders, excavators and water trucks onsite to carry out this work, without needing to engage an earthworks contractor to bring in traditional earthmoving equipment.

Through their fleets, mines also have greater ability to maintain infrastructure continually or periodically, and as geotechnical engineers, we build a suggested maintenance schedule into the operational plan.

Advanced technology changing the game

Technology advances in material testing are also enabling efficiencies.

When it comes to compaction control and uniformity, traditional testing methods can be costly and take time, with the potential to delay works, but knowing a material’s properties is vital to a project’s success.

Common industry methods, including the Nuclear Density Gauge, the Sand Replacement Method and the traditional Dynamic Cone Penetrometer (DCP) are well known and widely used, however each has its limitations, including time spent waiting for samples to be lab tested.

And if the material fails the test – it must then be removed, further impacting infrastructure deadlines.

Modern methods currently available including the Light Weight Deflectometer, Intelligent Compaction and the PANDA® Instrumented Variable Energy DCP, offering advanced processes and capabilities when conducting ground investigation, determining material stiffness and evaluating soil strength.  

Utilising these types of systems can:

• Enable continuous placement of material with confidence (without waiting for traditional test results).

• Reduce the risk of rework.

• Increase compaction uniformity.

• Increase layer thicknesses.

• Lower construction costs through cost savings and increased efficiency.

• Improve documentation and construction management.

For geotechnical engineers, working closely with mining companies to tailor infrastructure design to suit what’s available can reap benefits for all stakeholders.

Designing and conducting more efficient earthworks allows valuable hours to be reclaimed, to progress a project faster to its operational phase. And implementing the modern practices outlined in this article can also further balance quality, performance and costs through shifting what is traditionally capital expenditure (CAPEX) more to the operating expenses side (OPEX).

Through embracing the use of on-site materials and equipment, as well as advanced technology, and implementing a suitable maintenance schedule, key infrastructure should perform as required and last the duration.