Stresses around mine openings at depth can cause the surrounding rock to
fail, releasing stored strain energy. When this happens, the rock may
literally explode or `burst' into the opening without warning. As mining
progresses deeper into the earth, the possibility of seismic events and rock
bursts increases. Researchers at the US Bureau of Mines (USBM) are currently studying
seismic activity in three underground hard-rock mines in the United
States: the Homestake Mine, Lead, SD; the Lucky Friday Mine, Mullan,
ID; and the Sunshine Mine, Kellogg, ID. Waveforms from seismic events
are recorded by personal-computer-based hardware and software. This
information is archived and transferred from the mine sites to the USBM
via modem communication links. Then, using USBM-developed
software, the events are analysed to determine various parameters,
including magnitude, frequency, and location. In addition, researchers are modelling the deep levels of the Homestake
Mine using a finite-element code. These models generate stress and
displacement values for a given loading condition. By studying material
properties, in situ stresses, and seismic activity along with actual scope
sequencing, researchers can make correlations between stresses induced
by mining and the frequency and magnitude of seismic events. Information on seismic events coupled with results from finite-element
analyses have increased understanding of rock mass behavior and the
mechanisms that may lead to rock bursts. Optimisation of slope
sequencing designs as a result of these studies could reduce rock burst
hazards.