The client had engaged our sister company 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 the mine. As a means of validating the assessment a LiDAR scan was recommended. This would allow:
- Understanding the performance of the raise through multiple lithological units
- 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.
We deployed our Hovermap unit mounted to a winch. The unit was lowered down through the pilot hole to scan the entire length of the raisebore, and details of the completed scans were provided, which also confirmed the 90◦ rotation of the stress field in proximity to a regional fault. Assessment of numerical modelling criteria to compare forecast deformation against measured maximum overbreak was undertaken.
We provided a detailed scan along the raise plotting overbreak depths from 0.02m to 2m without slippage of the Simultaneous Localising And Mapping algorithm. Technical staff could assess that no liner was required with the detailed information provided.
The forecast empirical stability assessment indicated raise stability. The asbuilt although varying from significantly larger to just larger than the bored diameter showed that raise stability does not mean there is no overbreak. Results provided to site as point cloud, wireframe, sections, and analysis of rock mass response.