Geotechnical Monitoring
Over the past 10+ years I have been involved in the design and management of several geotechnical monitoring programs, both as part of a team and working with a team as an outsider. Designing and managing an effective geotechnical monitoring program is challenging. Below are 20 lessons I have learned through the years:
1. Define the purpose of the monitoring system
Geotechnical monitoring programs must be planned around the outcomes of the geotechnical design. Based on your initial geotechnical design, determine which excavations are at highest risk and focus on these areas.
2. Determine what will be measured (deformation, stress etc).
For the high-risk areas, determine which measurements will be the best indication of instability. If the expected failure is driven by the change of stresses (due to the planned stoping front) install stress meters etc.
3. Estimate the measurement ranges which are required (Deformation in mm-, cm-, m- or km-scale)
Once you have determined which areas require instrumentation, consider the expected ranges of measurements. Instrumentation requirements differ based on the required accuracy. Don’t opt for the most accurate instrumentation (if it is not required) as this will add unnecessary costs to your monitoring plan.
4. Whenever in doubt go for reliability
Whenever there is doubt about which instrument would be the best, choose the more reliable instrument.
5. Setup a TARP for different criteria
Once you have decided on your instrumentation system, setup a TARP (Triggered Action Response Plan) to ensure that whenever instrumentation readings go above/below threshold values, and action is triggered. This ensures that necessary actions happen as soon as it is required.
6. The purpose of each instrument must be made clear
An instrumentation plan can consist of many instruments, so it must be made clear in your documentation what the purpose of each instrument is, and how it fits into the geotechnical design plan.
7. If you don’t know, ask, it has likely been done before
If you are not sure about which instrumentation to use, ask around, it has likely been done before.
8. Set up an installation plan
Ensure that you have an installation plan set up prior to the instrumentation arriving. Keep in mind that involving more people in the installation process will increase the time it takes to install. Make sure the production team is aware of the importance of the instrumentation plan for both long-term safety and optimised mining.
9. If an installation is difficult, hire an expert to do it
If the installation of your instrumentation is difficult or the incorrect installation could make the data unusable, use an expert. It costs more in the short-term, but you will save in the long-term.
10. It always takes longer than you think
It is not uncommon for instrumentation to only be installed once it is too late in the mining schedule. To ensure that the instrumentation is in at the required time, plan up to 30% additional time for the installation process.
11. Instrumentation locations should be based on requirements, practicality and long-term reliability
Instrument locations are one of the most challenging parts of the design process. The location of instruments must be well thought through. General tips are:
Ensure it is installed in areas as required by the design
Locations must be practical. Don’t install instruments in the roof if it is not required, as you will require additional equipment for installation.
Consider long-term reliability. Don’t install instrumentation (including instrument cabling) in spots which will be damaged by boggers/muckers etc.
If the instrumentation must be read by a handheld device, ensure its easily accessible
12. Determine and measure all factors which can affect instrumentation (heat, humidity etc)
If your instrumentation is affected by site factors (heat, humidity etc) ensure that this is measured and the instrumentation readings get adjusted, otherwise your readings will not be reliable.
13. Set up a maintenance schedule with clear responsibilities
This is one of the most overlooked parts of the process. A maintenance schedule ensures that the monitoring system runs optimally, and downtimes are minimised. The geotechnical team should be responsible for managing and ensuring the maintenance plan is updated and adhered to.
14. Ensure you have checks and balances in place
Try and put as many checks and balances in place to double-check that instrument readings are correct. Instruments sometimes do fail or have defects, and you don’t want to use those readings.
15. Calibrate instruments
Instruments which can be calibrated, should be calibrated within reasonable time periods (drones etc) to ensure that no data drift occurs.
16. Budget for capital and running costs
When doing the budget for your instrumentation system, also consider the running costs of the instruments after installation. There will be repair, replacement and consultant costs over the duration of the instrumentation program.
17. Keep all your instrumentation documentation in one place
Staff turnovers can have a devastating effect on projects and therefore is vital that all documents, plans, TARPs and notes are kept in a centralised place so people can search for relevant information when it is required.
18. Database maintenance instructions
It must be clear how to collect data, and how it should be added to the instrumentation database. When instructions are not available or clear, the database becomes inconsistent and may cause difficulties when the data needs to be analysed. This document should also include the expected frequency of the data collection process.
19. Data integration
In the current digital age, the effective integration of multiple data sources into one main database is critical. Ensure that your instrumentation provider makes it possible to export data as a simple format from their software. Also remember, Dashboards are not the same as data integration.
20. Contracts are important
Having a simple but detailed contract with your instrumentation provider is critical. Remember that in many cases your instrumentation provider only has his best interest at heart, and therefore might not give you the after service required for the effective running of your instrumentation system. Ensure that your contract is clear on what your expectations are from the instrumentation provider, and what fines they might be liable to pay if they do not provide the required services.
Require assistance with your monitoring programs? Have many instrumentation databases, but not sure how to integrate the data into one centralised database? Contact us now for assistance. IGM Geotechnical, Underground Geotechnical Experts.