For geotechnical engineers working in mining having the latest in subsurface software innovation on board, to help uncover geotechnical complexities and make crucial decisions for safety and productivity, is imperative.
PLAXIS 3D enabled CCTEG Chief Scientist Wang Yong, and his research team, to successfully compute the complex interplay of soil and rock at the Laohutai mine, in China. We spoke with Seequent’s Miquel Lahoz and Pieter Neethling to find out more.
When multiple teams are working full steam ahead at one of the largest open-pit mines in Asia, rock mass stability will be a loaded topic.
“The Laohutai mine, in China’s Liaoning province, has some very complex geotechnical conditions at play,” says Miquel Lahoz, Product Manager, Geotechnical Analysis, at Seequent.
Mine trains induce strong vibrations as they carry massive volumes of material right next to the mine slopes and over two underground inclined shafts.
According to an article published by the scientific journal MDPI what needed to be determined was how the intense railroad vibrations could impact mine safety.
“It is quite unusual to have trains so close to the work area. These mine trains are only used internally, and standards allow them to be larger and heavier than conventional trains,” says Miquel.
“Consequently, they could have a significant impact on the safety of the slope and the tunnels excavated below,” he says. “Safety is paramount, and the concern is always the possibility of slope or tunnel failure.”
The Laohutai mine, in China’s Liaoning province showing (a) the outline of the mine site and (b) a section of road and railroad. (Image credit: MDPI)
Conquering geotechnical challenges
Using PLAXIS 3D software Yong and the research team created a complex numerical model to simulate the multi-sided interactions between the rail track, slope, tunnels and underlying geology.
With its innovative 3D modelling capability you can design and perform advanced finite element soil and rock deformation analysis. The team said they value PLAXIS for,
“Its’ solid theoretical base, user-friendly interface, and strong logic for analysis in almost any geotechnical engineering field.”
It is an integral part of Seequent’s world-leading suite of geotechnical analysis and information management solutions, that includes GeoStudio and OpenGround.
Miquel brings 6 years of PLAXIS expertise to his product management role at Seequent and understands the value our software can bring to these complex situations.
“PLAXIS can handle just about any geotechnical simulation project, whether it’s soil or rock or a combination of the two,” says Miquel. “And can account for nearly every aspect of geomaterial behaviour including stability and deformation under static or dynamic loading.”
Data-driven insights into engineering simulation
Geotechnical engineers are tasked with assessing the stability of slopes and underground structures to help prevent or foresee potential collapses, slips or failures.
“What’s required is the latest in data-driven innovation to support a robust assessment of the surrounding subsurface environment,” says Miquel.
Miquel works to ensure our software is developed in the best ways to help solve customers’ complex challenges.
“When I reach out to the teams engaged with our software, I want to learn more about their work, their success and also to better understand their challenges,” he says.
“And communicate this to our researchers and developers so we can put more refined, enhanced software into the hands of our customers.”
To understand the geotechnical challenges at the Laohutai mine is to recognise a very multidimensional soil and rock mechanics scenario. At several kilometres wide, the mine is enormous, but the focus of this geotechnical analysis was on a smaller area of concern – 200 metres long by 120 metres wide – around the two tunnels.
“The mining railroad runs on the surface next to a slope and crossing over two inclined shafts, that are essentially tunnels,” explains Miquel. “The tunnels run through a weak chlorinated rock layer and are subject to the consistent vibrations of the heavy passing trains.”
The complex upper gravel, sandstone, weak chlorinated and bottom sandstone layers modelled in PLAXIS. (Image credit: MDPI)
Uncovering geotechnical complexities
PLAXIS is a built-for-purpose geotechnical analysis software that enabled the team to capture all the structural interactions and simulate the complex behaviour of both the topsoil and rock underneath.
Miquel says they achieved stellar results, “Their predictions were validated with measurements taken on-site and the slope was found to be stable with a safety factor of 1.2 and well above the Chinese mining standard threshold of 1.05.”
“They found a maximum displacement in the gravelly topsoil of about 5 millimetres, which is small and to be expected if the rock formations underneath are stable. In addition, the impact of the load vibration both on the slope and the inclined shafts was minimal and the weak rock layer, in the context of the overall analysis, was not an issue either.”
PLAXIS not only helped the team assess the dynamic effect of train vibrations on the slope and tunnels, but also understand the influence of various geological features such as the topsoil gravel, underlying sandstone, and weak chlorinated rock.
A safe mine is a profitable mine
“Across the globe, not one mine site is the same and as a geotechnical engineer there’s so much that mining throws at you,” says Pieter Neethling, Segment Director, Mining Operations at Seequent.
“From different geological complexities and nuances to other naturally occurring challenges such as seismic vulnerability.”
Pieter brings over 30 years of experience in the mining industry to his role at Seequent and understands safety is paramount.
“We must always consider how to best keep our teams, equipment and the operation safe,” he says. “And that means having a better understanding of your surrounding environment.”
Unlike construction materials where everything is well understood and under control, there are many more aspects to consider with variations in rock properties.
“Having the right data and innovative tools such as PLAXIS behind you to create detailed geotechnical models, helps ensure a thorough assessment of the complex mechanical behaviour of soil and rock,” says Pieter.
“At the Laohutai mine the two inclined shaft tunnels act as crucial portals to the whole operation,” he says. “It’s imperative to keep the tunnels open and the mine operational economically and most importantly – to keep it safe.”
A finite element model in PLAXIS showing the position of the two inclined shafts successively going through each different rock layer. (Image Credit: MDPI)
Empowering geotechnical engineers in mining
The value of the MDPI research for geotechnical engineers is seeing PLAXIS in action to help solve such complex stability and stress-strain analysis-type scenarios.
Comparing the analysis results with in-situ monitoring greatly enhanced the researchers’ trust in PLAXIS, finite element analysis, and their numerical model of the site.
“It’s a great test and we get a lot of learning and confidence when the results are robust and they validate the factor of safety,” says Pieter.
“And even when results vary there’s still value as we can ask what more is needed to push the boundaries and build out our technology to better deal with complex industry challenges.”
Want to learn how PLAXIS can better support geotechnical engineers in mining? http://www.seequent.com/products-solutions/plaxis/
Want to try PLAXIS?: https://go.virtuosity.com/plaxis-trial