What is a Borehole Extensometer and How Does it Work?
What is a Borehole Extensometer?
An extensometer is a measuring device designed to measure changes in the length of a specific object. When mounted in a fixed position relative to a bank of soil or a rock face, extensometers are capable of measuring displacement (movement) with a high degree of accuracy.
Borehole extensometers (e.g. SMART MPBX) are specifically designed to fit easily in a standard size borehole; for example, the type drilled out in order to install stabilizing cable bolts. Multiple extensometers can be fitted into the same borehole (decked) if required.
Some extensometers, like those in the MDT SMART Cable Bolt, are actually fitted inside a regular 7 strand cable bolt, allowing the same borehole to be used for monitoring and support.
How Does It Work?
A borehole extensometer used in a mining context is usually placed in a borehole drilled into the wall or roof of a tunnel, an open rock face, or a crown pillar on surface. The instrument is then fixed solidly in place, most commonly with grout. In this configuration, the extensometer provides data about rock and ground movement in the surrounding rock mass.
This data can provide an early warning of displacement that could lead to a collapse. These devices are therefore very important as a safety measure. They also help to prevent production disruptions, as potential problems can be reported and addressed before they become more serious.
Data from individual borehole extensometers can be read manually using MDT’s SMART Reader, automatically using MDT’s SMART Log or SMART Log3, or in real-time using the MineHop wireless mesh network with MDT-RTU’s and Ethernet Gateways.
Data is available directly to mine engineers logged into the network via the mine’s existing LAN infrastructure. Data is interpreted and made available via custom software (e.g. the MDT MineMonitor or MineHop packages).