Case Study 03
Raisebore Examination 1km Below Surface
Western Australian Gold Mine
The client had engaged MineGeoTech to undertake the geotechnical design assessment for a 4.5m diameter ventilation raisebore between 1045m and 1208m below surface to assist development of a new area of the mine. As a means of validating the assessment a LiDAR scan was recommended.
Understanding the performance of the raise through multiple lithological units would assess the requirements for a liner for long term stability.
Calibration of empirical stability forecasts against actual performance for stress state with a k-ratio of 3.
MINELiDAR deployed their Hovermap unit mounted to a winch. The unit was lowered down through the pilot hole to scan the entire length of the raisebore.
The detail of scan along the complete raise provided
Confirmation of 90deg rotation of the stress field in proximity to a regional fault
Assessment of numerical modelling criteria to compare forecast deformation against measured maximum overbreak
Part of the raise with stress spalling and parts of the raise with stress induced damage to structure
Validation against site seismic system
Assessment of drillers comments on face stability and empirical face stability
Comparison of empirical stable diameters with overbreak depth and overbreak areas
Observation of buckling on one side of the rise and minor fall out on the other
Assessment of the influence of penetration rate on seismicity and overbreak
Lithological controls on overbreak