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Mapping the Underground World

Critical technology for intelligent mines

The future of underground mining

The way we work is changing. Advanced technology tools are transforming the way we collaborate, analyse, organise and innovate. In just about every sector, the tech advance is helping organisations be more productive, save time and money and work better together. And the mining industry is no different – only that it lags behind. (1)

With increased competition, the pressure is on. Around the world, mining operators across all commodities are facing the combined challenges of declining ore grades and operating efficiency. With the decreasing availability of tier one assets, and continued focus on shareholder returns, operators are looking towards digital tools and new ways of working to drive results.

The digital revolution can transform and automate the entire mining value chain from ‘pit to customer’. Advanced supply chain visualisation tools can aggregate data from multi-systems to show near-real-time operations metrics; drones can help with geotechnical monitoring and remotely conduct stockpile volumetric audits; and powerful laser scanners can build highly accurate 3D maps of underground mines in minutes.

The last decade has seen the rollercoaster of highs and lows in the mining sector; and the volatility is likely to continue.(2) While digital tools are readily available that help mining decision-makers do the job better, faster, safer and more cost effectively, there are still many businesses slow to embrace transformative practices. With change being a constant, forward- thinking mining operators need to embrace digital technology and drive innovation, or risk being left behind.

As the mining industry’s value proposition is increasingly called into question, mining companies are beginning to see that they cannot succeed into the future unless they change the way they operate.

-Glenn Ives, Americas Mining Leader, Deloitte Canada

The old tools are blunt

Today’s mining companies aren’t short for choice when it comes to assessing ground-breaking technologies. From autonomous vehicles to automated drilling and tunnel boring systems, the decreasing cost of technology puts many of these innovations within reach. Even within the last few years, drone technology has taken off to the extent that easy-to-use aerial technology is now affordable – and millions of drones are sold each year. (3)

Digital technologies already employed or that will be employed in the next 3-5 years in mining operations:

How spatial data visualisation is rocking the mining world

According to Anglo American, spatial data is being used more and more in the mining industry, with spatial data models and maps becoming more detailed and clearer than ever before. Today, we are seeing breakthroughs in three-dimensional (3D) modelling, Virtual Reality (VR), and Augmented Reality (AR) technology.(1)

3D modelling creates a viewable, life-like impression with depth perception that allows the human brain to understand and relate to complex interrelated issues. VR enables a user to test a piece of equipment without the risk of damage or cost. These new technologies allow us to design new mines more efficiently and make it possible to experience what it’s like to work in a mine without being out in the field.

Digital technologies can not only help mining companies survive, but importantly, to thrive. The productivity and safety gains of embracing new technologies are huge: better equipment performance (47 percent), operational/administrative cost savings (42 percent) and better decision making (40 percent).(3) When you add in stronger collaboration across the supply chain, safer conditions for employees being removed from dangerous working conditions and waste being eliminated – even the most risk averse of mining companies can be convinced.

Yet to be truly successful – cutting-edge technology alone isn’t enough. While digital solutions will empower employees to make better decisions, they will also cause upheaval as manual jobs are automated. Mining companies need to consider how to create new employment opportunities, and how to reskill and retrain people to learn technology and tools faster. They’ll need to not only reach beyond traditional tools but importantly embrace the mindset and approach to collaborate.

Technology is certainly not a silver bullet, but targeted in the right places, it will make mines even more safe, and our operations more efficient and cost-effective.

– Dr Caius Priscu, Head of Mineral Residue Facilities, Anglo American

Rio Tinto: Mine of the Future

A decade ago, Rio Tinto declared one of the most ambitious transformation programs in mining: plans for an intelligent mine packed with driverless trains, trucks and robotics. At the heart of the program is an operations centre in Western Australia that today generates 2.4 terabytes of data every minute from hundreds of pieces of mobile equipment and sensors. Covering 16 individual mines, the one integrated centre (which looks very similar to NASA’s control centre) is manned by operators over 1,500km from the physical sites.

The mining giant was also the first mining company to introduce fully autonomous haul trucks which to date have moved over 1 billion tonnes of material and travelled over 150 billion kms. But automation doesn’t stop there: it also introduced automated drills in production drilling, which is safer for operators and more efficient, and is introducing robotic automation in its rail system – a train comprised of 244 cars stretching a total of 2kms driven by robots. Next stop, possibly a mine with no miners?

The challenges in discovering the world beneath us

We’ve long been fascinated by the underground world of tunnels and caves, and with today’s tech it may soon be possible that ‘Google maps™’ goes underground. Yet aside from exploring the depths for knowledge, mine operators need to safely tap into and excavate the wealth of minerals beneath us. And this comes with a number of challenges:

Access Issues
Access Issues

Underground mapping is one of the most difficult and demanding forms of surveying with mining professionals needing to work in tight, enclosed spaces.

Hazardous Sites
Hazardous Sites

Mining sites are notoriously hazardous, despite the most rigorous safety checks. Companies strive for zero-harm targets yet the mapping process itself is risky.

Pressure to Optimise
Pressure to Optimise

Tunnel construction and underground projects are time consuming and complex, and companies need to plan efficient site operations to optimise production cycles.

Time Constraints
Time Constraints

Mining professionals need to rapidly and accurately map underground environments under intense time pressure, yet traditional survey techniques are slow and inefficient.

Transforming mapping in mining environments

Access to user-friendly technology that can quickly scan difficult-to-reach environments and produce accurate and high-quality 3D data can be a game-changer for mining operators. Leading the change is 3D mobile mapping which helps mine operators improve the way they dig up commodities as well as helping them cut costs, all without the need for GPS.

Using a handheld laser scanner, operators can walk and scan, or attach the scanner to a trolley, drone, pole or mine vehicle for remote monitoring of hazardous environments. The scanner collects the data and SLAM (Simultaneous Localisation and Mapping) software turns it into actionable 3D information within minutes. With minimal training, operators can use it for rapid insight into rock mass behaviour, to measure stockpile volumes or to map complex tunnel profiles. Robust enough to deal with extremely harsh environments, laser scanners help mine owners deliver productivity and efficiency improvements, at the same time as keeping operators safer.

This technology allows us to quickly and easily view, compare and evaluate data to paint a picture of what’s under the ground. It’s like an ultrasound image of the deposit delivered in real time, something that we could never do before.

– John McGagh, Head of Innovation, Rio Tinto


What exactly is SLAM?

SLAM stands for Simultaneous Localisation and Mapping. SLAM devices take data from sensors to build a picture of the environment around them and where they are positioned within that environment. The complex SLAM computations and algorithms effectively construct or update a map of an unknown environment while simultaneously keeping track of the device’s location within it. Every few seconds, the scanner is comparing the data collected with the last few seconds and aligning familiar features together to create a very accurate point cloud.

Setting a new standard for the mining and natural resource sector

Creating highly accurate maps of the underground world, for the mining and natural resource industries, is one of the most complex forms of surveying. Yet innovations in laser technology are transforming and simplifying the way we map the world beneath us and are being applied to a wide range of applications including:

Tunnel & Underground Mine
Tunnel & Underground Mine
Stockpile Analysis
Stockpile Volumes
Shotcrete
Shotcrete
Convergence Analysis
Convergence Analysis
Shaft Inspection
Shaft Inspection
Production Progress Mapping
Production Progress Mapping

With powerful mobile mapping technology at their fingertips, mine operators have ready access to previously unattainable insight into rock mass behaviour. This means they can better tailor their ground support regimes, monitor convergence and better target rehabilitation areas. Other benefits include:

Rapid scanning
Rapid scanning

Operators can slash survey times with easy-to-use technology. Anyone on site can map accurate tunnel profiles, stockpile volumes, pits and caves in minutes.

Go-anywhere mapping
Go-anywhere mapping

You can use the technology in the trickiest, darkest and dampest of spaces, even where GPS isn’t available. Walk with the handheld or attach it to a trolley, drone, robot or autonomous vehicle.

Safety as a priority
Safety as a priority

You can safely scan underground, inaccessible and dangerous environments, even remote and hazardous areas.

Save time and money
Save time and money

Data capture and modelling are up to 10x faster, allowing you to successfully complete projects in minimum time with little or no disruption.

Case Study

Mapping hazardous mines under intense time constraints

Beck Engineering, an Australian mining engineering consultancy specialising in mining and rock mechanics analysis, needs to rapidly map mines under intense time constraints using versatile technology which is adaptable to any environment. GeoSLAM’s handheld mobile mapping solution was chosen as it is compact, portable and delivers a high level of accuracy. With GeoSLAM’s “go-anywhere” 3D technology in hand, Beck Engineering has been able to supply invaluable data regarding the direct effects of mining to better understand the implications of a deforming rock mass. Beck Engineering is now able to accurately measure the shape of an excavation or tunnel over time. As a result, tunnels are safer, better designed and more cost efficient.

We have continued to use GeoSLAM products as they have proven to be affordable, lightweight and sufficiently robust devices for their application underground. GeoSLAM continues to produce a high-quality device that is at the forefront of practical mobile laser scanning devices.
– Evan Jones, Senior Rock Mechanics Engineer at Beck

Tech advancements are already helping improve mine safety, remove wastage and drive greater productivity. And mining companies are already creating jobs that require artificial intelligence or automation-specific skills – from data scientists to automation engineers. Forward-thinking operators who foster innovation will remain competitive. While some mining companies may hesitate and deliberate choosing which technology is best for them to deploy, others are decisive and lead in the race for intelligent mine of the future.

The digital revolution is here – and it’s going underground. With unmanned technology able to carry out open-pit operations, and complex software algorithms able to mine vast quantities of sensor data, the leap to a truly digital mine is within reach.

References

  1. Future Smart Mining – Anglo American
  2. Tracking the Trends 2018 – Deloitte
  3. Drone Sales Have Tripled – fortune.com

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Scanning Shotcrete in Mining

Improving quality assurance & quality control whilst reducing costs

The history of shotcrete

Since its conception in the early 1900s, shotcrete application has developed to become one of the most critical ground supporting techniques for underground excavations.  The technology has evolved from manual nozzle handling to computer guided, hydraulically controlled boom-mounted nozzles.  By controlling variables in the shotcreting application, the layer of sprayed concrete can be optimally designed to meet the in-situ geotechnical constraints.  In some scenarios, shotcrete will be designed to flex with the squeezing rock, whilst in others, it may simply act as a barrier to protect from rock bursts.

Understanding how the shotcrete will react in different conditions allows operators to apply the right amount of material.  Shotcrete thickness is paramount when applying shotcrete, therefore it must be monitored during application using the safest and most reliable method.  The aim of this article is to demonstrate how the SR-50 system, developed by GeoSLAM, is suitable for near real-time shotcrete application quality assurance and quality control (QA/QC).

Shotcrete – The modern method with failing processes

The Sika Sprayed Concrete Handbook (1) states that the only method for accurately calculating initial strength is by measuring thickness.  Current methods rely on operators endangering themselves to un-secured shotcrete in order to manually collect thickness readings.  A total of 5% of all tunneling injuries can be attributed to the shotcreting process in tunneling (2).  Industry professionals recognise the need to balance the provision of a safe working environment for its operators with the demand for increased production rates, accurately measured and documented shotcrete thickness.

In 2016 GeoSLAM developed the SR-50 system deployed throughout the Jetcrete Australia fleet.  The technology has now been licensed to Normet Oy who have adopted the technology as SmartScan.

SR-50 System
SR-50 System
SR-50 Software Interface
SR-50 Software
Interface

The system provides the operator with near real-time results displaying shotcrete thickness after each application cycle with a single button press.  A colour-coded map of the spray area allows the operator to identify regions of concern easily and accurately.  Once the operator is satisfied that the sprayed thickness complies to site criteria an electronic report is automatically created.  This report documents the application cycle, providing the average applied thickness, total volume of shotcrete applied to the surface and the final thickness map that can be used for quality assurance.  All data is stored on the system for further analysis and archiving.  Without exposing the operator to dangerous conditions, the system can act as a training tool for novice operators, as well as aiding experienced operators to spray to the desired profile thickness, thus minimising overspray.

Analysis of data collected from sites using the SR-50, showed an approximate 20% reduction in overall concrete usage.  This means that an average single sprayer operation can reach a return of investment within 2-3 months, have improved safety, and expedite the shotcrete application process.

The system created by GeoSLAM now achieves an accuracy of less than 5mm.  This measured accuracy and reliability of measurement now enables the large-scale use of the technology on multiple sites.

The need to modernise

Traditional methods for measuring shotcrete thickness are based on invasive in-situ sampling at discrete points.  Samples are taken either, when the shotcrete is freshly applied, e.g., Fibercrete Depth Indicators (FDI’s) or once the shotcrete has fully hardened, e.g.  ASTM C174 drill core test.  In both cases these methods have been shown to be unreliable and disruptive to the work cycle.

Fibrecrete Depth Indicators (FDI)

FDI’s are used by inserting “shotcrete stamps” into freshly applied shotcrete using the boom of the spraying rig. An investigation carried out at Olympic Dam in 2018 concluded that FDI’s were incredibly disruptive to the operation as well as poor measurement technique to represent the whole heading (3). For a typical profile heading with a cut length of 4.0m, the surface area sprayed was approximately 55m2. 20 probe sites were sampled, resulting in a sample area of approximately 0.05m2, or just 0.0009% of the sprayed surface.

Drill Core Tests

Where drill core tests are taken most sites typically only manage to measure samples to the nearest 10mm, and again there is an element of bias towards where these drilled samples are taken from along the profile of worksite. Aside from an unsatisfactory sample size and potential for bias, the above methods either have the potential to damage the spray rig boom or are conducted hours after spraying, so any issues are not resolved at the time of application which result in time delays and extra costs.

There is an increasing trend in tenders and contracts throughout the shotcreting industry, requiring that shotcrete thickness be accurately measured and documented across the whole sprayed surface. Therefore, new, and novel methods must be used to meet the contractual obligations whilst minimising the disruption to the work cycle. The use of Laser Scanning technologies can meet these demands by providing non-invasive measurements at the time of application; sample points that can run in to the hundreds of thousands, overcoming sample bias; all taken in a handful of minutes immediately after the application meaning that any remedial action is taken immediately.

Laser Scanning: Accuracy benchmarks

Terrestrial Laser Scanners (TLS) and Scanning Total Stations (STS) systems are based on laser technology and are commonly used across numerous surveying sectors where accurate range measurements are required.  Typical systems have accuracies that range from sub-mm to several mm’s depending on the underlying technology and cost.  However, in the underground environment these technologies tend to be extremely expensive, complex to use, often requiring specialist training, and can require time-consuming processing in an office environment to produce results.  The SR-50, although based on laser scanning technology was specifically designed for the shotcreting industry to be simple to use, automated, cost effective and accurate.  

To evaluate the accuracy of the system a rigorous approach was developed.  The assessment criteria relied on the use of a TLS (Riegl VZ-400) that was deployed in a controlled environment.  The TLS was chosen on the premise that to assess the accuracy of the SR-50, the reference data must of greater accuracy than the test data.  The ability to control any changes in the environment was paramount to avoiding ambiguities in the results.

An artificial tunnel environment was constructed with cross-sectional dimensions similar to those in the mine tunneling environment.  After an initial base scan of the environment, using the TLS and SR-50 a series of control-panels of known thickness (verified using vernier callipers) were introduced at varying positions in the tunnel.  After each control-panel was introduced, changemaps were calculated from SR-50 and the TLS data. Thicknesses of 8, 13, 18 and 30mm were used.

The Results

The first assessment of the SR-50 system was to compare comparison results of the test environment with no change against the results using the TLS. Since, there was no physical change to the environment this provided an indication of the repeatability of the system. This assessment was then repeated by placing 8mm, 13, 18 and 30mm boards into the scene and measuring the average thicknesses using the SR-50 and TLS data.

The top image shows the comparison map derived from the SR-50 when no change was made to the environment. The middle shows a comparison of the computed changemap from the TLS control-panel (LHS) and the panel measured by the SR-50 (RHS), both for a 13mm control-panel. The figure clearly shows that the SR-50 gives comparable results to the TLS. The changemap for the TLS gives a more consistent result due to the much higher point density. However, the measured average change across the panels are the same. Control-panels were also attached to the sides and shoulders of the test area and an example changemap is shown in the bottom image.

Board Thickness (mm)081318
Smartscan Selection Mode Difference (mm)0000
Third Party Difference (mm)0111

The above table provides results for the comparison between the average thickness of the control-panels measured using the TLS and SR-50. To assess the accuracy of the automated changemaps created in the SR-50 software, the raw data was exported and thickness maps were calculated in a 3rd party software. The results show good agreement with the on-board solution available at the time of spraying.

Conclusion

By using laser technology and scanning the working area before and after shotcrete application, shotcrete thickness is automatically calculated across the complete working area in near real-time.


To provide an initial assessment of system accuracy, a series of measurements were undertaken in a man-made, controlled area. A series of control-panels of known thickness were introduced into the environment and thickness maps calculated by the SR-50 were compared to maps created using a Terrestrial Laser Scanner of much higher specification. Additionally, the results automatically created by the system were compared against results created manually in a 3rd party software package.


The results showed that thickness maps created using the SR-50 system were comparable to a TLS system. Average control-panel thickness was typically within 1-2mm between the two systems. The investigation shows that the SR-50 is accurate and reliable enough for the shotcreting industry. When comparing to the inaccurate in-situ measuring the industry has previously adopted (such as the ASTM C174 drill core test), the SR-50 can provide reliable results across the whole sprayed face in near-real time. The system is able to:

Provide an accurate thickness report every time a spray is required

Drastically reduce shotcrete wastage by helping the spray application process in achieving its desired thickness in a single attempt

Ensure geological ground control is achieved and upheld during the full shotcreting operation

Help nozzle-persons gain experience in spraying by providing near-real time thickness results.

As shotcreting becomes more common in mining and infrastructure projects around the world, the industry needs to evolve to accept the need for strong QA/QC methods and reporting in near-real time.


References

  1. Sika Services AG. (2020). Sika Concrete Handbook. Available: https://www.sika.com/content/dam/dms/corporate/t/glo-sika-concrete-handbook.pdf. Last accessed September 2020
  2. Kikkawa N, Itoh K, Hori T, Toyosawa Y, Orense RP. Analysis of labour accidents in tunnel construction and introduction of prevention measures. Ind Health. 2015;53(6):517-521. doi:10.2486/indhealth.2014-02
  3. Unpublished site report: Olympic Dam, BHP, 2018.

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