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Last Updated on 11th May 2023

The role LiDAR plays in convergence analysis

What is convergence analysis in mining?

Convergence analysis is the process of repeatedly inspecting areas of an underground mine to track changes in the rock. The goal of the inspections is to better understand the rock’s behavior, and to take action when it’s becoming unsafe. Such problem areas include fractured rock masses and tunnel deformation.

It plays a key part in the safety of the mining sector. It monitors the structural integrity of mines and tunnels, excavations, and infrastructure assets. With convergence analysis, tracking and measuring changes or displacements that have arisen is possible. Keeping track of detected faults or hazards is crucial, therefore data collection must be accurate and easily repeatable – LiDAR plays a vital role in the data collection for this analysis.

What are the benefits of monitoring convergence in the mining sector?

The main benefit of convergence monitoring is risk management and staying up to date with significant underground hazards.

Structural Integrity of Mines
Structural Integrity of Mines

Convergence analysis increases safety in mines as collecting accurate information on faults lessens the risk of collapse.

Increasing Workers' Safety
Increasing Worker Safety

Mines take safety very seriously and regular inspections of the tunnels is vital for protecting the workers and limiting the risks to human life.

Detecting Hazards Earlier
Detecting Hazards Earlier

Up to date data helps to maintain the productivity as hazards are detectable before becoming a major problem in the mine.

What factors affect the stability of rocks?

When the stress that the rock mass is subjected to is greater than the strength of the mass itself, it negatively affects stability.

What causes rock failure?

Rock failure occurs when there is a deviation in composition, pressure, and temperature in the surrounding environment. Rock failure encompasses both fracture and flowage in the rock mass. Mining operations can unintentionally cause ground instability because of the digging and explosions that occur during operation.

Rock deformation factors by regions

Another factor affecting rock stability is geographic location and types of materials mined. Rock deformation can differ based on the region, country or material mined due to the geological characteristics of the rock formations. For example, certain locations that feature elevated geological activity or proximity to bodies of rock that contain groundwater can contribute to rock stress.

Mined material

Mining metallic ores like gold or copper is different from mining materials like coal. The result of this is a difference in the amount of stress applied to the rock, due to the patterns they leave behind after excavation.

Natural disasters

Countries prone to natural disasters like earthquakes or landslides have a higher risk of rock deformation in their mines. For instance, earthquakes can cause sudden movements and fractures of the rock, resulting in convergence or deformation patterns.

Excavation Regulations

Mining techniques and regulation vary from country to country, which can impact the methods used to control convergence. Some countries have strict regulations on mine design or excavation methods that could affect rock behavior differently to other countries.

These factors mean that a requirement for regular checks may differ per country or per mine, depending on the impact their activities have on the rocks. Subsequently, some mines may need regular updates on the deformation and others less so. Mobile SLAM solutions offer a way to capture data whilst minimising the impact on daily production, therefore daily, weekly or monthly data capture is viable.

Rock deformation, instability, and failure

The amount of movement, as well as the rate of movement, can inform the mine operator of the optimal time to rehabilitate the subject section of the excavation. When the amount of convergence approaches the inflection point at which it becomes a risk to mine safety or production, the mine operator can plan for rehab works, rather than react to an emergency resulting from unchecked deviation.

What is tunnel deformation?

Within mining, tunnel deformation can develop for two reasons. It can either occur when the ground becomes displaced due to weather conditions, erosion, or an overload of pressure. Additionally, it can happen when the tunnel’s structure, such as concrete lining, moves unpredictably. Tunnel deformation can create cracks within the rock formation, which in turn causes groundwater loss and puts the safety of a mine at risk.

How convergence analysis informs tunnel deformation monitoring

Measuring convergence works by mapping the tunnel wall-to-wall, capturing data of the area. Comparing regular collection to the original data allows teams to track change and evaluate when adding reinforcements is necessary. Mobile LiDAR is an ideal tool for this job because it provides fast and accurate data collection.  Regular comparisons of the 3D data in software such as Point Studio or Void Mapper provide surveyors with the relevant data for informed decision-making.

What is Mobile LiDAR used for in Mining?

Mobile LiDAR has had a vast impact on the mining sector as surveying is faster, safer, and more productive. The versatility of LiDAR makes it useful for a variety of applications within the mining sector, from increasing processes and advancing workflows to ensure the safety of workers and the mine itself.

Benefits of LiDAR for convergence analysis

Both mobile LiDAR and static LiDAR have distinctive uses and benefits for applications within the mining sector. With the increasing demands of mine production, the benefit of documenting progress without disturbing production provides a major cost saving.

Mobile LiDAR

The biggest benefit of mobile LiDAR is its simple deployment, as the hardware is easy to use and lightweight, providing an ideal tool for fast data capture. This means there is a limited effect on the mine’s productivity. Mobile laser scanners make convergence analysis easily repeatable, which allows for quicker decision-making, in turn, leading to increased time/cost efficiency and safety.

Static Scanning

A common method of LiDAR data capture, for convergence analysis, is static scanning. The data gathered is highly accurate and ideal for those in need of more granular data. If the convergence monitoring requires millimetre accuracy, then static LiDAR would be the preferred option.

An efficient way to collect information on faults within mines is to use both mobile and static LiDAR, as they complement each other. The repeatability of scans is crucial for convergence analysis, combining multiple methods of laser scanning widens the capacity to capture information.

The ease of use and time efficiency of mobile LiDAR means scans can be conducted more frequently to collect regular data on any concerns within the mine. Then, when necessary, capturing significantly more accurate data of recognised fault areas is possible using static scanning. Using the LiDAR scanners in conjunction with each other has the potential to increase productivity and the speed of mitigating instabilities.

In summary

Over the years, LiDAR solutions have provided access to previously difficult-to-obtain information on rock deformation in mines. The accuracy and repeatability offered have made mining safer and more profitable. The research and development of mobile LiDAR technology has increased in recent years and early adopters are beginning to see the separate benefits it brings.

Though most mines are still using static scanning to understand the spaces around them, a combination of mobile and static scanning provides a bedrock for efficient data capture. They complement each other providing surveyors with speed, accuracy, and fast returns on investments. Additionally, mobile LiDAR has proven to be an ideal solution for a variety of surveying activities in mines, not just limiting itself to convergence analysis.

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