title of the thesis - Department of Geology - Queen's University

Chapter 1
Introduction
1.1 Background
The stress system in the mining environment is a result of the superposition of pre-mining and
mining-induced stresses. When this stress exceeds the strength of the rock mass, failure occurs.
In the dynamic mine environment, impulsive changes in the stress field caused by blasting or
more gradual stress perturbations, from excavation for example, can result in failure. The
excavation process in hard rock mines results in stress concentrations in which strain energy is
accumulated (Beck et al., 1997). Strain energy in a rock mass can be dissipated by local rock
fracture or plastic yield, transferred to support, retained as elastic strain, or less favourably,
radiated as seismic waves emanating from unstable failures such a fault slip, crushing and
cracking (Beck et al., 1997).
Seismic monitoring is used to observe this last category of strain release and has become an
integral part of the mining process. It is of primary importance for the safety of underground
workers and for uninterrupted mine operation. Monitoring seismicity can also help track the
physical state of the rock mass over the long term (Alcott et al, 1998; Szwedzicki, 2003; Coulson
and Bawden, 2008). The onset of seismicity can signal the commencement of rock mass damage
and yield (Falmagne, 2001) and high event rates and dense event spacing suggest progressive
damage of the rock mass (Vasak et al., n.d.; Falmagne, 2001).
Seismicity that is located remote to mining is often attributed to geological structure. Structures
with high elastic parameters as compared to the host rock are capable of storing more strain
1