Monitoring Mine Infrastructure (Pt. 1)

Manmade mining structures above and below ground geologically change over time and hence need to be monitored for integrity and stability. Even closed mine sites require continuous attention to safely avoid long-term mining-inflicted damage.

Ensuring integrity and stability of tunnels, shafts, spoil heaps, tailings dams, slopes etc. requires deformation data from soil and rock beds together with hydrological information. Decentralized sensors gather the raw information, and a central server processes data from all sensors extracting desired insights. But how does the data get there?

Technicians still travel to mine sites and stay there for measurement campaigns. They connect sensor interface units and power for the duration of a campaign. Sensor data is stored and uploaded to the server upon return from the mine. The approach only generates snap shots apparently while incurring significant cost though.

Continuous monitoring would yield significant better insights. Trends could be detected earlier resulting in faster and more pointed counter measures if and when needed. Stable mining structures - the basis for safe operation and prevention of mining-inflicted damage - could be achieved much more efficiently.

Continuous real-time monitoring is possible today. Solutions are relying on components from different vendors that are not necessarily compatible though. This results in system integration risk and unclear budgets and time lines.

Vibrating Wire Sensors are most common in Mining. They measure mechanical forces, strains, deformation and temperature accurately and precisely with good long-term stability.

Data logger devices gather sensor data directly. Companies like rst instruments, WorldSensing and Geokon have specialized here. They offer battery-operated wired or wireless solutions. Depending on the sample frequency and choice of battery data loggers operate uninterrupted from some weeks to several years. Consolidated data gets transmitted to a gateway device which connects to a central server through the Internet.

Bild 1: Sensor Data Acquisition (Courtesy WorldSensing S.L.)

Networks around data loggers and gateways follow a start topology as shown in figure 1. Gateways provide the wide area connection that enables monitoring from anywhere in the world. Connectivity specialists like Campell Scientific, MaxStream (acquired by DigiKey) and Sierra Wireless offer various gateway products.

There is no common standard for processing sensor data. Analytics and dashboards are often custom-made for certain use cases. Vendors such as Canary Systems and Navstar offer software packages for mining applications. Figure 2 shows part of the eco-system.

Bild 2: Fragmented eco system for mine site monitoring.

Engineering services companies support planning and implementation of mine monitoring solutions as system integrators. This adds to the upfront cost for equipment purchases (CAPEX). Amortization may take several years. Expansions require additional capital. 

In summary: Sensor based safety solutions for continuous mine monitoring require an eco-system of sensor manufacturers, data logger and gateway vendors and system integrators. A rather fragmented offering of system components causes significant overhead for planning, implementation, bring-up and maintenance. This adds cost and causes schedule-related risks. The prevailing business model has mining operators purchasing the solution. As a result they carry both operational expenses (OPEX) and upfront cost (CAPEX). 

Innovative market entrants promise to reduce capital expenditures by introducing per use business models in conjunction with simplification of installation and handling. We are going to discuss these offerings in one of our next blog posts. Stay tuned!