Some Common Types of Geotechnical Monitoring Instrumentation Used In Underground Mines

Various types of geotechnical monitoring instrumentation are used in mines to monitor geomechanical behaviour and other factors that have the potential to impact safety and productivity.

• Contractometer: Used to measure stresses that develop in rock or soil, usually because of convergence or compression (loading or settling). Typically, contractometers have a collapsible structure, inside which is one or more sensors that measure contraction of the structure due to stress placed on it by convergence or compression in the area around the instrument.

• Multi-point borehole extensometer (MPBX): Measures displacement and settling of rock or soil (along a single axis). Modern MPBXs usually feature up to six reference/anchor points and an electronic readout head.

• Instrumented cable bolt: Cable bolts are used to provide support and stability to rock faces. In underground mines, they are commonly found in the walls and roofs of tunnels, caverns, stopes, and other areas where extra support is needed. An instrumented cable bolt is a combination device that consists of a miniature extensometer fitted within a standard cable bolt.

• Ground movement monitor (GMM): As the name indicates, this device monitors ground movement. GMMs are usually installed within primary support areas of a mine, where they provide a cost-effective, instant monitoring solution.

• Sloughmeter: Used to monitor caving (or sloughing), e.g. around a stope. Sloughmeters work by containing an internal circuit, which is broken if the area into which they are installed collapses.

• Thermistor string: Monitors ground temperature in underground mines.

The value of geotechnical monitoring instrumentation is fully realized when these devices are connected to a wireless mesh sensor network, providing an easily-accessible, accurate bank of data that allows mine engineers to monitor the status and behaviour of rock, soil, and other geological and topographical features in the mine.