The quest to understand dam site conditions has traditionally combined intrusive investigations (test pits, penetration tests and boreholes) with testing on site, followed by laboratory testing of recovered samples.

Dr Peter Chapman, Technical Director, Tailings, says that although the traditional methods can yield good information, there are challenges. “Intrusive tests take time and can be costly. Some locations are difficult to access or have high cultural or environmental sensitivities that restrict vegetation clearance or ground disturbance.”

However difficult it is to expose the secrets that lie beneath the surface, a full appreciation of the vulnerabilities of the site is fundamental for preventing dam failures. For tailings storage facilities (TSFs), the importance of a thorough understanding of the site – including geomorphology, geology, hydrology and geotechnical performance – is emphasised in the recent Global Industry Standard on Tailings Management.

Dr Tariq Rahiman, Technical Director, Geophysics, explains that poor site characterisation may not recognise the potential for geological abnormalities. These can include faults/fracture zones, sinkholes or karsts, paleochannels, duricrusts, and unstable geological materials such as expansive or cohesionless soils and seams, and low-strength weathered strata. Other geological concerns are related to ground permeability and seepage.

“It's also vital to understand the potential for naturally triggered events such as earthquakes, landslips, high rainfall and flooding, including their likelihood, magnitude and consequences,” he says. “In a changing climate, the risk position of the facility from climate-related events needs to be continually reassessed.”

Testing methods reveal site conditions

Newer geophysical technologies and methods are providing solutions to support design, construction and management of tailings facilities.

“Contemporary geophysical surveys are non-intrusive so they have minimal impact on the survey area and can be used where intrusive methods are not viable,” says Tariq. “Geophysical equipment is versatile and can be adapted to fit the survey extents and access restrictions. The equipment is set up manually and generally consists of low-powered electronic equipment, without the need for heavy machinery, therefore offering greater operator safety.

The greater coverage of geophysical testing yields more data and addresses understanding of the lateral extent and changes of subsurface layers.

However, Peter explains that traditional and advanced methods aren’t necessarily mutually exclusive and a combination of methods may be an effective solution. “Geophysical testing can be used as a complement to other methods and data, and as a supplement rather than a substitute. Undertaking geophysical testing can give a quicker, cheaper and greater overview that can then be used to identify particular locations where it will still be useful to drill.”

WSP at the cutting edge of geophysical technologies

Advanced and innovative geophysical technologies are continually evolving. These are some of the tools and techniques WSP is applying for clients across Australia:

“WSP is an industry leader in applying advanced geophysical methods for obtaining subsurface information,” says Tariq. “We are building a successful track record using these innovative investigation methods to solve project-specific challenges for our clients and to deliver value for money with higher quality and quicker results.”

Peter notes that TSFs are always evolving across their lifecycle, and international practice continues to improve. “We want to stay at the forefront of changing methods and technologies to give our clients and communities greater confidence,” he says.

“It’s imperative that the mining industry takes every action possible to prevent TSF failures, which can be extremely harmful and have long-lasting impacts on downstream communities, biodiversity, land and waterways.

“Mining critical minerals will be fundamental for our clean energy transition and new green materials, and it can be safe and sustainable if supported with the best information and understanding that smart technologies can deliver.”

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