In situ stress estimation using acoustic televiewer data

摘要

A good understanding of stress in deep, high-stress mine environments is of critical importance to geomechanical modelling, mine design and ground control. Stress is traditionally a challenging and expensive measurement, and the available methods produce sparse data that are subject to high levels of uncertainty. In this paper, the authors present a method for obtaining principal stress orientations and constraints on relative magnitude from acoustic televiewer (ATV) breakout data. The method uses breakout orientation data from multiple deviated boreholes (from horizontal to vertical) across a volume of interest. This method assumes the volume is homogenous and linear elastic to calculate the theoretical location of breakout along each borehole. Next, a global optimisation algorithm steps through all possible stress states until it finds the global minimum, which minimises the angular residual between the observation and theory. ATV data is continuous, and thus the stress state resulting from this method is supported by hundreds of observations. Lastly, the authors present the results from a case study at a deep mine in Sudbury, where breakout data from 10 boreholes (horizontal and sub-vertical) were used to calculate the principal stress orientations. These results were discussed and compared with world stress map results.