In shaft mining, a boring machine drills vertically into the earth to gain access to minerals beneath the surface. Shaft mining is generally more environmentally friendly than strip or open pit mining since only a small area is affected by digging. To protect the surroundings, it is critical to monitor underground water streams and mineral (potash) resources while works are being carried out.
Shaft mining requires strict control over the quality of work and materials. High-performance concrete, optimal working conditions and the weather are all moving pieces in the quality control puzzle. Where liners are required, the compression strength of concrete is critical before removing forms. Yet every hour that can be shaved off removing the forms to move on to the next section translates into large savings for the contractor.
In a major project in Canada, the site conditions made it difficult to install and protect devices throughout the excavation. The design called for a liner for the shafts to be built from the bottom up. Constraints on concrete volume, work schedule and underground conditions made it essential to have accurate knowledge of the properties of each pour.
The challenge was that the concrete cylinders produced for quality control had to be cured at the surface, at temperatures exactly matching temperatures measured 900 meters underground in real-time.
Worldsensing partner GKM Consultants was mandated to design, deploy and commission a large-scale concrete cure match solution for the construction of the shaft liner.
The innovative monitoring solution that GKM Consultants developed and introduced uses custom-made Geokon 3800 thermistor arrays connected to 350 Worldsensing vibrating wire five-channel devices. Measurements are taken automatically from the start of the pour and are transmitted wirelessly via the Worldsensing devices, gateway and CMT Edge, to an on-premises data analysis platform. These measurements are then relayed back to the surface, where a control system takes individual thermistor readings and redirects them as setpoints for GKM’s C3-Match curing boxes. It has proven possible to maintain the temperature of the concrete cylinders within 2°C of the in-shaft forms at all times.
The Worldsensing in-shaft devices are low-power, long-range LoRa nodes that can read the thermistors continuously for months and transmit the data wirelessly back to the platform, no matter what depth. Additionally, this wireless infrastructure can be upgraded to integrate structural health monitoring instruments such as strain gauges or extensometers.
From Worldsensing’s CMT Edge, the monitoring data is integrated with a data visualization platform through MODBUS TCP. The software provides real-time alarms if any of the temperatures are out of range, if temperature gradients are too large or if communications are lost with any of the instruments. It also provides real-time plotting capabilities of the in-shaft concrete forms and concrete cylinder temperatures. A custom tool was developed to calculate and plot maturity curves for each pour in real-time, giving crucial insights to engineers and project managers.
Watch the video here on how wireless monitoring improves concrete curing in shaft mining.
Thanks to the monitoring technology, the curing process, including the type and amount of concrete used can be optimized. Since concrete adds greenhouse gasses to the atmosphere, the project’s carbon footprint can be reduced by properly optimizing the curing process.
Furthermore, the solution is able to save time and money with click-and-connect deployment of the Worldsensing data loggers and gateways as well as a smooth software integration with CMT Edge and a third-party data visualization software through MODBUS TCP.
Working with a reliable, wireless monitoring solution translates into low maintenance costs and effort.
Finally, the Worldsensing solution provides autonomy and agility when having to re-deploy and configure devices in the network.
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