Experiment using the HICell for stress measurements in a Utah coal mine

This thesis is concerned with the measurement of in situ stress state and the interpretation of data obtained from instruments such as the US Bureau of Mines borehole deformation gauge and the Australian Commonwealth Scientific and Industrial Research Organization Hollow Inclusion Stress Cell (HICell). Both are installed in long pilot holes and overcored to relieve the stress state. Gauges which are bonded to the end of a borehole such as the South African Council for Scientific and Industrial Research "doorstopper" are not considered. The data reduction formulas for calculating the stress state are based on a solution first obtained by Hiramatsu and Oka. Pariseau proposed an alternative solution in 1984. This alternative solution has since proved to be correct. The data reduction scheme for the HICell is not affected since both solutions are based on the same state of stress and strain. Data reduction is not affected for instruments which measure change in diameter of a borehole, but it is affected for those which measure axial displacement. The error due to the conventional formulas is dependent on the initial stress state. An experimental investigation of the correctness of these solutions was attempted under laboratory conditions. Also, the HICell was tested in a Utah coal mine for use as an absolute stress measurement instrument as well as a stress monitoring device.