For many underground mines, convergence monitoring plays a crucial role in day-to-day safety and productivity monitoring.
Up until the development of the mobile convergence monitoring workflow using the uGPS Rapid Mapper™ product, a quick measurement at spaced intervals was the typical status quo. Some customers have recognized the need for enhanced convergence monitoring techniques over large areas and not just point-to-point measurements. This is especially true for areas where there is significant human exposure, such as extraction levels and main haulage networks. In these areas, a need for more regular and detailed convergence monitoring was highlighted.
There are two major reasons for this:
- In high-stress areas where there is a lot of mining activity, large vehicles, drilling, and blasting by miners can cause disturbances in the surrounding rock mass and initiate some deformation — or convergence — which is a strong indicator of a potential rock fall or collapse.
- Many modern underground mines have grown quite large, with many hundreds of kilometers of open ground — and they continue to expand every day. Conventional point-to-point measurements are very time consuming– so much so that some mines cannot realistically monitor all relevant areas in a continuous and repeatable manner.
With this in mind, many underground mines already have convergence monitoring measures in place in working or high-traffic areas. Often this takes the form of an array of contractometers embedded into the walls and roofs of tunnels, stopes, drifts, and other affected areas. This method yields good results in short periods of time, especially where the instruments are monitored and data extracted my means of a wireless mesh-sensor network.
However, there are also limitations to this approach, as each sensor only monitors a small area and a lot of data must be gathered and analyzed to form “the big picture”.
A very useful tactic now being used by some underground mines is to employ a faster method of convergence monitoring by using 3D mobile mine scanners, like the uGPS Rapid Mapper.
The uGPS Rapid Mapper™ 3D mobile mine scanner can be mounted on a vehicle and driven through the mine, rapidly creating a bank of accurate data as it goes.
This can supplement the convergence monitoring information gathered from installed instruments (helping to make the mine even safer) or be used as the primary source of data in areas where no instrumentation is installed, e.g. during mine construction or expansion.