Estimation of in situ stress from borehole breakout for improved understating of shaft overbreak in brittle rock
During deep tunneling or mining infrastructure development, the assumed stress state has significant implications on geomechanical design. Remote measurement of the three dimensional stress state at depth has proven to be a significant challenge and is often assumed from historic tests or the regional tectonic setting. This paper presents a stress estimation methodology using numerical modelling of brittle rock, which allows for the back analysis of breakout profiles from a shaft pilot hole at KGHM’s Victoria Project in Sudbury, Canada. By iteratively changing the horizontal stress ratio and maximum tangential wall stress, a set of generalized curves relating breakout characteristics (breakout depth and opening angle) and borehole strength along the 2 km borehole were made.