Rock-solid equipment for rock mechanics testing
As our lives are conducted above ground everyday, rarely are we concerned about what lies beneath the Earth’s surface. But when digging tunnels or excavating mines, soil and rock mechanics suddenly become a key consideration. Trilab in Brisbane, Australia, part of Kiwa Group’s Intega family, leads the way with state-of-the-art triaxial testing equipment.
How does a rock mass perform at various depths? What effect would that performance have on excavations like tunnelling or caving during the mining of precious materials like copper, gold and other metals? Materials that are used for computer chips and other technology components that help us operate our day to day lives.
The answer lies in rock triaxial tests. These tests obtain accurate results in determining the mechanical properties of rock cores, when they are sampled from substantial depths below the Earth’s surface. The results allow engineers to continuously improve designs for caving, tunnels and open pit mines.
These tests simulate the stresses surrounding the actual rock sample whilst in the ground and allow the strength of the rock to be determined as if it was still in the ground surrounded by the accompanying rock. As projects in these areas can run into the billions of dollars, accurate testing is seen as a way of minimising the risk profile.
Large mining projects from around the globe have a high demand for rock triaxial testing services. Trilab is one of only a few laboratories worldwide, capable of performing tests for various strength parameters. Operating in such a niche field, samples are received from all over the world.
Oyu Tolgoi, Mongolia. Photo © Rio Tinto.
One example is the Oyu Tolgoi project in the South Gobi Desert of Mongolia. It is a combined open pit and underground copper mining project. Starting in 2010, the mine has now reached its maximum capacity delivering over 400,000 tonnes of copper annually. As well as copper, the site also produces gold and silver. The project has entailed the testing of hundreds of samples on an ongoing basis, to help determine the strength parameters of the rock mass for the mine design moving forward. Currently, Trilab receives monthly pallets of samples delivered from Mongolia, as there is nowhere else in the world where large volume materials testing can be performed on the specialised rock triaxial equipment.
As Oyu Tolgoi is forecast to have a mine life of decades, future testing requirements for this project are immense. Even more so, as relatively new mining methods such as block caving are being used. This method is deemed to be considerably more efficient than conventional mining processes: a large portion of rock is undercut, forming an artificial cavern which is filled with debris as the rock collapses. This broken ore falls into a series of access tunnels constructed at the base of rock, where miners can continuously extract the ore. To allow safe block caving, mine designers must obtain as much information as possible on the properties of the rock mass.
Oyu Tolgoi, Underground, Mongolia. Photo © Rio Tinto.
Not your average equipment
Trilab has been performing rock triaxial tests for over 30 years and commissioned its first high capacity rock triaxial machine in 2014. To service increased demand from mining and civil construction clients, another custom-built machine was added in 2021, which allowed for quicker turnaround times for test results.
The machines are not considered standard laboratory equipment. “They are only supplied by specialist equipment manufacturers, and can take up to nine months to build. But, they are well worth the investment”, says Colin Purvis, Trilab’s Area Manager. “The majority of specialised rock testing in our industry is performed in repurposed concrete testing equipment which can be quite unsuitable for these high strength testing needs. This is due to the testing machine deforming under the high stresses required to test samples to meet customer requirements. Custom-built equipment is necessary to obtain accurate results. Usually, machines like ours are only ever found in research establishments or universities. We were lucky enough to redesign and adapt these machines for commercial use.”
For specialised testing services like Trilab’s, analysing and deciphering soil and rock material is a key factor in allowing the subsequent project works to be conducted in the safest and efficient manners possible. To test what lies beneath the ground, is the first step in ensuring that life above ground can continue as normal.
Test engineer from Trilab testing rock samples using the Triaxial machine.