The importance of building a robust geotechnical program

Tim Cartledge, Principal Consultant, Cartledge Mining and Geotechnics

Mine site safety depends on many factors, with a crucial component being a robust geotechnical program. Tim Cartledge, Principal Consultant at Cartledge Mining and Geotechnics, recently spoke to delegates about this topic at the Mongolia Mining 2024 International Mining Expo, held in the natural-resource rich developing country.

In this article, he shares his expertise on why robust geotechnical plans are so vital, what’s at stake when there are shortfalls and how the industry can implement solid plans and embrace opportunities to drive towards a safer future. 

We’ve all heard the statement, “a chain is no stronger than its weakest link”.  

This is particularly true in mining, where safety is paramount, and the stakes are inherently high. 

Failures can cause fatalities. 

Large, unexpected and uncontrolled movements of ground can bring tragic outcomes; not just financial implications, but also potential loss of lives. 

Such critical exposure requires robust geotechnical programs and it is vital geotechnical engineers understand how to create them, and why. 

Along with the potential for fatalities, there are multiple impacts, and gaining an understanding starts with looking at what else we miss if no such program exists: 

• Increased waste mining: If a comprehensive geotechnical study has not been completed, the plan and your implementations are guesswork. It can be difficult to know if you are being too conservative, or too aggressive. Sub-optimal design can result in increased costs and CO2 emissions. Without a detailed understanding of how the ground is going to perform, it’s hard to know where the opportunities are for the project. 

• Difficulty accessing funding: With an ever-increasing global focus on best practice and international standards (including JORC reporting in Australia), there is a rising requirement to implement geotechnical programs and have a competent geotechnical engineer sign off on reserve statements, or JORC statements, to be able to obtain funding.  

• Loss of licence to operate or jail: Lacking diligence in the implementation of a geotechnical mining program can be costly. Globally there have been many cases of mine licences lost, and people jailed, and this is not where any mines – or geotechs – want to end up.  

Quality data capture at the core of every robust plan 

The nature of the geotechnical design process is not linear. Through each stage, from the models, through domains, design, analyses and implementation, the process is iterative and not something that is just done once, and all the issues are found. You build on it and get the data as you go through. 

Data collection is pivotal to a geotech’s role, it’s something we all do, and must do well if we are to develop a robust geotechnical program. 

It’s imperative we are collecting all data required to develop our models, across the four geotechnical constituent models – geology, structural geology, groundwater and rock mass. Each one of these could impact the project in a different way, and each project has varying impacts and influences that control the geotechnical performance of a site. 

A multitude of data collection methods can be used: geotechnical drilling, field mapping, geophysics, etc. Geotechnical data collection can be an expensive and time-consuming process, so it’s vital to ensure there is value in the process, and a lot of data is being captured at once. For example, when conducting geological drilling, capture geotechnical and ground data then, too. It’s about spending wisely. 

Quality assurance and quality control are key data collection considerations. Recent experiences on projects in Australia and overseas have highlighted issues including, have the personnel been trained correctly, and have they gone back and validated all past data?  

Large databases exist, but when we go back to check data quality and adherence to process, often we have had to disregard the old data as it either had not been collected at all, was incomplete, or its interpretation was incorrect. 

It’s crucial geotechs are certain the data used in designs is robust, verified and validated. 

Data capture is an ongoing, layered approach and it takes time. Design confidence increases through design stages and with data availability. Confidence levels progress as you move through the mine design phases – from Concept to Pre-Feasibility Study, to Feasibility Study, to Design and Operation. 

This staged process allows us to improve and develop our understanding, provide targeted drilling and data capture techniques and make sure money is spent wisely as we move forward while reducing mining risk. 

When looking at capital cost risk, as we progress through the design stages, the risk of capital costs blowing out and risks to project reduce as data confidence levels increase.

Implementation, hazard management and beyond

While around the world we are seeing positive implementation of some parts of geotechnical programs, there is still opportunity to improve and ensure programs are robust, authentic and complete.

When implementing plans, geotechnical hazard management is a key contributor to success – it’s all about managing geotechnical risk when out in the field, keeping operators safe and reducing the risk of financial failures.

Identifying and communicating about hazards is crucial, which comes back to that support system and processes that make sure everyone is on the same page and doing the right thing. This includes following a Ground Control Management Plan (GCMP). All monitoring programs should also be linked to Trigger Action Response Plans (TARPs) for cohesive action.

Drill and blast optimisation is also fundamental, as effective blasting manages geotechnical risk and improves mining rates.

If drill and blast aren’t right, the implications are broad; mining rates go down, walls can be damaged, and the potential for risk and mining waste increases, so CO2 and financial costs go up, all affecting mine economics.

Monitoring is another key part of the system, which comes at the end of the process. A plan should be developed based on geotechnical knowledge and experience.

While standard monitoring processes are implemented as part of a geotechnical program, ground conditions must first be understood, and questions asked, including, what hazards are we trying to monitor, and what are the controls we could put in place?

Instrumentation includes slope stability radars, prisms, groundwater monitoring, extensometers and inclinometers. But we are not providing an effective program if we don’t understand the conditions and the structure.

The monitoring strategy – tactical versus strategic – also comes into play. Tactical is about short-term, day-to-day operations and short-term live monitoring, such as radar use to monitor walls.

Strategic monitoring is more long term, looking at defamation patterns and how the ground is responding, which feeds back into the geotechnical model.

Reporting is paramount, through understanding and monitoring trends to identify potential geotechnical hazards. Geotechnical engineers must look at data regularly, to identify anomalous trends, and then report on that, making sure that if something is identified, action follows.

It’s imperative to be ahead of the game, not just reacting when defamation or instability develops.

Reviews and feedback are also important, but not always completed effectively.

The design process is very circular. The biggest exploration tool we have is the void created in the ground – we can go out and look at that and obtain so much information that can be fed back into the program, to improve drill and blast, wall performance, and reconciliation, and ensure mining is at a safe level.

As geotechs, we must create that loop.

The benefits of a robust and effective geotechnical program

If we have a robust and effective geotechnical program we are looking after our people, providing a safe workplace, with reduced potential for unexpected ground and slope failures.

We are improving economics – with lower CO2 emissions – and we are also looking through a lens that tells us if slope angles are too shallow, or voids are too small. With a proper plan, we can then act – to optimise design and ultimately reduce the amount of waste, improving the financial performance of the mine while keeping risks in check.

Improved safety equals less risk of unexpected failures.

Improved economics equal lower CO2 emissions and optimised slope designs.

Improved investment potential equals confidence in the mining reserves.

With strength and integrity of work, geotechnical engineers can ensure all these vital links in a complex chain maintain the same properties, too.