Slope instability is one of the major concerns in open pit mining. Significant collapse of the pit wall can result in injuries or fatalities, damage to mining equipment, interruptions to production and potential loss of reserves. Properly interpreted microseismic data can be used to augment surface monitoring systems in identifying potential instability and the associated failure mode. A challenge for this microseismic application is that many seismic events associated with slope movements are weak and they hardly trigger a microseismic monitoring system that is set up to record an event in a trigger mode. A research project carried out at an open pit mine in Australia used both trigger mode and continuous mode to record microseismic events. The preliminary results have shown that the weak events are equally important as the strong seismic events for slope stability assessment, and they should not be ignored in microseismic monitoring for open pit mining.
Maintaining slope stability is a major task for open pit mining and civil engineering. Microseismic monitoring techniques have been recognized as an efficient tool to map rock fracture network development for slope stability assessment (Hardy and Kimble 1994; Lynch and Malovichko 2006). Properly interpreted microseismic data can be used to augment surface monitoring systems in identifying potential instability and the associated failure mode. This technique has been used for identifying potential failure locations (Trifu, Shumila, and Leslie, 2008), estimating potential damage scales and unstable volume (Wesseloo and Sweby, 2008), and prediction of impending failures and improving understanding of how mining affects the pit stability (Lynch et al., 2005).
Microseismic monitoring techniques measure seismic signals generated from rock breakage or movement inside the open pit. As microseismic sensors can measure rock fracture events remotely, these techniques are capable of mapping the 4D pattern and dynamic development of rock fractures before any deformation on the slope surface can be observed.