Issue link: https://geospatial.trimble.com/en/resources/i/1482400
December 2020 www. .com 19 MINE SAFETY This is an example where manual monitoring (also called periodic or campaign monitoring) is the most effective way to monitor deforma- tion, performed by a surveyor on at least a daily basis. Once the surveyor collects the measurements, the data must be processed – checked for errors and against previous data points – before the detection of a potential failure (i.e., landslide or collapse) and decisions around miti- gation of an impending hazard can be made. For surface mines, a short-term project on a site with reliable com- munication services and clear lines of site across the project might be well suited with manual monitoring. However, large and long-term sur- face mines present the perfect opportunity to employ automated monitoring (sometimes referred to as fixed or real-time monitoring) to predict slope stability. This type of system provides a constant data set, in real time, rather than relying on snippets of data collected periodically. It also offers additional safety measures that are not realised in a manual set-up. It is important to note that auto- mated does not mean maintenance free. An automated monitoring sys- tem keeps a constant watch on the thresholds established for extreme temperatures, ground velocity, dis- placement data or data gaps, and when those are exceeded, project stakeholders are engaged to make necessary adjustments. Having experts on site who know what to do with the data is key to the success of any monitoring system, manual or automated. WHAT INSTRUMENTS COMPRISE A MONITORING SYSTEM? Manual monitoring systems generally consist of a total station and an RTK Global Navigation Satellite System (GNSS) receiver. These are the tools a surveyor needs to collect deformation data, which is then added to either a spreadsheet managed by the surveyor or input into a software program that automatically analyses the data. An automated system relies on the same basic set of equipment in addition to prisms and geotechnical sensors. Depending on the commu- nication options available on-site, additional hardware may be needed. All of these pieces together will measure and collect the data needed to watch for trends over time that could help predict a failure. The final piece of an automated system is the software program used to collect and analyse the data. Following is a list of hardware and software options to consider when building a monitoring system: • Total stations: The workhorse of a monitoring system, total stations are an optical instrument used to measure angles and distance. The Trimble S-Series stations are ideal for a dusty mine environment because of their frictionless drive. The patented Trimble MagDrive (magnetic-driven) technology prevents wear on the instrument, as opposed to instruments with motors that tend to wear out in harsh environments. • Prisms: To acquire accurate meas- urements, total stations measure to prisms. Manufactured to high precision, they provide reliable targets for total stations to make accurate and repeatable measure- ments. The number of prisms needed depends on the size of the project as well the type of mining. Some very large opera- tions can have hundreds of prisms in a single pit. • GNSS receiver: They collect highly accurate location data, which is critical to a mining operation that is watching for any changes in the landscape. • Geotechnical sensors: Necessary to collect different types of data such as tilt, distance or angular deflection. Geotechnical sensors complement positional data by providing high-precision and high frequency measurements for specific variables. In mining envi- ronments, these sensors are used for structural monitoring of tail- ings dams and mine walls as well as collecting environmental data for weather, hydrology, and soil measurements. • Communication devices: These are used to connect sensors to software. Several options are avail- able to address project conditions and requirements. From unreliable to non-existent cellular or internet connectivity to hills that block vis- ibility between total stations and servers, there are challenges in the mining environment when it comes to reliable communication. Technology such as the Settop M1 data collector helps to overcome these obstacles. • Software: The right software will connect all the dots, informing project stakeholders in real time of potential risks, increasing the opportunity to mitigate situations before they become a catastrophe. Trimble's platform for real-time displacement monitoring – Trimble 4D Control (T4D) – configures optical, GNSS and geotechnical sensors, manages monitoring data, applies geodetic corrections, reports, visualises and shares analysis with project stake- holders. T4D also generates auto- matic alerts when predetermined thresholds are hit. The mining world is certainly no stranger to deformation monitoring. But it can be difficult to determine the right monitoring system. When selecting a monitoring system, ask the questions posed in this article to protect people, production and the environment. *Jesse Huff is Trimble Monitoring's regional sales manager for the Americas and Asia-Pacific. Jesse Huff, Trimble Monitoring's regional sales manager for the Americas and Asia-Pacific Trimble S9 total station at a copper mine in the Democratic Republic of the Congo