FAQs: PRIME Technology
ITM Monitoring - now SOCOTEC Monitoring - showcased an innovative new earthworks monitoring technology, PRIME, at the Institute of Civil Engineers in London.
PRIME was developed by the British Geological Survey (BGS) Geophysical Tomography Team in close collaboration with a steering group of industry experts. Professor Jonathan Chambers – Principal Geophysicist and Leader of the BGS Geophysical Tomography Team answers some questions about the technology.
In this first iteration, PRIME is a remote condition monitoring tool. In future, there will be more opportunity in terms of early warning and failure detection as a greater database of cases is built up and the geophysical information gained allows us to better understand the link between precursor processes to individual failure events.
We refer to PRIME information delivery as near-real-time. It can take around an hour for the subsurface scan to be completed. Then you need to allow time to transmit the data back, to process it and to extract the movement information. At present, PRIME does not provide an immediate indication of what is happening on site. This is why we can’t currently rely on PRIME as an immediate failure detection system.
The resistivity technique is entirely scalable. You can deploy it with sensors separated by just a few millimetres looking at very small-scale processes or, it can be deployed with survey lines of a mile in length, with 20 metre separation of sensors. In general, the longer your imaging line or grid, the deeper you can see. The rule of thumb is that imaging depth is approx. 20-25% of line length.
There is a trade-off, however. The system uses a finite number of electrodes, currently the system can address 256. If you spread these sensors out, then you can achieve greater penetration and greater coverage but, as you spread sensors out, the spatial resolution decreases.
The typical installation runs off a fairly small 40w solar panel and for nearly all of the monitoring applications, this is sufficient. Where mains power is available, we will use it, however. Again, there is a trade-off. If we run the system continuously, then the solar panel power set up would not be enough but, for many of the application we are dealing with, one or two scans per day is sufficient and the power set up we have is configured for that.
The system is configured to generate regular health logs, informing us on how the system is operating. These health logs are streamed back from the system using the telemetry so we can monitor very carefully how battery levels are being maintained. If we identify any problems we can either modify the monitoring scheme to preserve battery life or we can go out and service the system.
By using a GRP enclosure, our intention was to make the system as inconspicuous as possible, for it to blend into the background. We’ve had a dozen or so installations over the past year and we’ve only had an issue of theft at one of the sites, where the solar panel and the batteries were stolen. Our learning from this was to install the solar panel some distance away from the system enclosure, so that opportunistic thieves don’t necessarily make the link between the solar panel and the enclosure.