As CPB (cemented paste backfill) backfilling becomes more common in underground mines, new techniques and practices develop to make this activity safer and more effective. One practice that is starting to gain popularity is locating piezometers directly within the area that will be filled with CPB, in order to measure pore pressure of the CPB as levels rise and stopes fill up.
Due to its high moisture content, CPB behaves in much the same way as a thick liquid until it settles and cures. Liquids can sometimes behave in unpredictable ways, and a sudden flow into a particular area or in a particular direction can cause significant pressure– for example, against a specific area of a stope wall.
Measuring the pore pressure of the CPB in different areas is essential to understanding its stress state and the amount of stress it is likely to place on surrounding structures and geological features. For example, piezometer monitoring to compare barricade, brow, and mid-stope pressures can give mine engineers valuable insight into CPD behaviour and whether certain parts of a barricade or wall are at risk of collapse.
Armed with this information, they can then take action to address the risk and keep backfill operations running smoothly and safely.
To make the data measured by vibrating-wire piezometers located in the CPD fill zone easily and rapidly available, a wireless piezometer monitoring system should be used.
One of the key components of a good piezometer monitoring system is a series of wireless nodes, like the MDT VW-RTU, which gather data from each individual piezometer and then loop it from one node to another until it enters the mine’s LAN via an Ethernet gateway and becomes easily available to mine engineers.