Characterising rock mass changes using multiple geophysical monitoring techniques

A key challenge for underground rock mechanics laboratories is to identify and develop the proper techniques to characterize
rock mass changes and to monitor the processes under study. The International Fault Slip Control Research Initiative (IFSCRI),
being led by the Centre for Excellence in Mining Innovation (CEMI), aimed at conducting underground experiments to improve our
understanding of what controls induced and triggered seismicity. A preliminary project is dedicated to the development and
testing of monitoring techniques that could potentially capture stress and strain field changes as well as characterize rock mass
degradation processes (fracturing). A prerequisite to monitor rock mass change is to have techniques and methodologies
available that present a high repeatability index when nothing changes. In this project, the rock mass changes of a 150m x 100m x
30m volume in a crown pillar will be monitored while it is being mined out. The stress, strain and rock mass changes induced will
be captured by a dense borehole array, heavily equipped with various geophysical tools. The contemplated techniques include
deformation measurement using multi-point borehole extensometers, micro-seismicity monitoring, noise and seismic tremor
analyses, seismic tomography, borehole logging (televiewers, sonic logs and other physical properties logging), cross-hole DC/IP,
an accelerometer network and strain measurement using optical fibers. This communication presents the experimental design
process involving the anticipation of the rock mass response during mining. Initial data collection targets testing of the
applicability of the proposed techniques and the evaluation of their repeatability index.