SLOPE STABILITY
technology offerings, and the quality of the support that they have provided and continue to provide to our team. Our radar operators unanimously agreed that GroundProbe’ s high quality software solution, SSR-Viewer, was unparalleled in terms of analysis and interpretation of slope monitoring data.”
GroundProbe says it will now work to deploy the suite of radars to site, and looks forward to the continued support they will provide to the Samarco team, working together to ensure that no further movement goes undetected.“ GroundProbe is not just a provider, but a partner,” Carneiro said.
Another relatively recent example of GroundProbe providing safety-critical monitoring for a tailings dam was in September 2014, when a tailings dam failure occurred at Herculano Mining’ s Retiro do Sapecado open pit mine. The team at Herculano Mining needed a rapid response to secure the safety of their staff, and ensure such a failure would never again go undetected. With GroundProbe’ s dedicated team in Brazil, stocked with a lease fleet of slope stability radars, Herculano Mining could rapidly collect the data they needed to restore safety on site.
Following the accident, Herculano Mining immediately responded by acquiring GroundProbe’ s SSR-XT to further monitor and assess risks during reinforcement work in affected areas, as well as desilting three tailings dams. Herculano Geotechnical Consultant, Antonio Augusto, said the radar is now imperative for site operations:“ I think it would be impossible to operate the cleaning of dams without the presence of the radar.”
The radar is stationed on a frontal position to the area where the slide occurred. A complete inpit alarming solution was also developed between GroundProbe and Herculano Mining, which worked alongside new site procedures, to ensure site evacuation occurs when an alarm is raised. Moreover, the data collected in Brazil is uploaded and checked each day, by one of GroundProbe’ s geotechnical engineers in Australia, who produces a daily report that highlights operational risks as they occur.
A place remains for LiDAR
Although it is still one of the most dangerous sectors to work in, the mining industry has potentially seen the most revolutionary improvements in worker safety. All mines and quarries strive to create the elusive‘ zero-harm’ workplace policies, but in an environment where heavy machinery and challenging working conditions are commonplace, there are still injuries and fatalities each year.
Dr Neil Slatcher, Research and Development Manager at 3D Laser Mapping told IM:“ While many deaths and incidents are caused by
machinery and poisonous or explosive gases, slope failure is one of the most feared occurrences in both an underground mine and an open-cast operation. There are many causes of slope failure – rock mass strength, stress, pore pressure and even the presence of unknown geological features that can weaken walls and cause small deformations, as well as critical failures. Early warning systems are vital when it comes to saving lives. In 2013, the incident at the Bingham Canyon Mine in the US represented the largest non-volcanic landslide event in the history of Canada and the United States. Some 65-70 million m 3 of matter collapsed into the open pit. Miraculously, no injuries were recorded, thanks to the prior installation of an interferometric radar system that forewarned of the event and allowed the operators to close down operations prior to the incident.”
Interferometric synthetic-aperture radar systems( InSAR), use images from two or more radar scans to replicate a surface, using the variances in the phase of the waves returning to the unit to measure differences in elevation or surface deformation. Changes can be monitored using time-series scans carried out week-byweek and year-on-year. Slatcher adds, however,“ InSAR systems have been a great aid to open pit mining operations such as Bingham Canyon, yet are only truly valuable when used on a large scale. Synthetic Aperture Radar( SAR) uses phase-based technology to measure change, therefore displacements must be no more than one wavelength in size to be detected and measured. Light Detection and Ranging( LiDAR) technology works in a similar way to radar, yet uses pulsed light from a laser to capture surface detail in the same way.”
He says LiDAR systems are seeing a great level of adoption in a variety of sectors due to their ability to map and measure differences in the landscape down to millimetre accuracy. For monitoring purposes, changes are determined based on a constant speed of light and the time measured between emitted and received pulses.“ Although radar can cover a large area, LiDAR can give a better understanding of slope dynamics, both pre and post failure. The correlation between small rockfall events and large-scale
Ranging( LiDAR) technology works in a similar way to radar, yet uses pulsed light from a laser to capture surface detail in the same way
slope failure has been debated and proven by research teams across the world. Hundreds of studies have been carried out using radar, LiDAR and other remote sensing techniques to help predict when rockfall events may escalate to a critical level. The one common theme is that continual monitoring is critical to be able to prevent a catastrophic event taking place.”
He adds:“ These types of early warning systems don’ t just save lives, they also save operators time and money in terms of closures, machinery replacement and restitution pay-outs. Earlier this year, an avalanche was triggered by extreme weather conditions in Pakrut, Tajikistan. A gold mine in the local area was submerged by consequent flooding, bringing operations to a standstill. Work is not expected to restart until the first quarter of 2018, with an initial insurance claim submitted for $ 9.2 million by operator China Non-Ferrous Gold Ltd. This is a prime example of how preventative measures could have saved operators a vast amount of money and profit.”
But despite LiDAR technology having the potential to revolutionise the mining industry, operators still have a responsibility to make sure employees are fully aware of health and safety policies. And Slatcher argues that although it’ s impossible to predict exact outcomes using any type of sensor, a new mindset is needed to utilise the technology now available to monitor all types of hazard.“ All legal mining operations monitor air quality and gas levels, with which there has been a reduction in fatalities, yet slope mechanics are often overlooked when it comes to making data-driven decisions in a mine. Both LiDAR and radar offer decision makers the ability to monitor the structural health of a mine site for benefits to both safety and efficiency. Care also needs to be taken to minimise the impact of the extractives industry on the environment. LiDAR mapping can, and has been used to assist with environmental impact assessments prior to any work taking place. It’ s also possible to use timeseries scans to create topographical maps of the
70 International Mining | AUGUST 2017