Geotechnical modelling, classification and exploration for safe and efficient mine layout and tunnel support design

Developments and improvements in geotechnical modelling, classification and exploration for safe and efficient mine layout and tunnel support design were achieved through rock mass classification, rock testing, underground measurements, seismic system development, improved numerical modelling techniques and application at field study sites. In geotechnical modelling, new constitutive models were proposed for rock creep and stiffness properties. Further advances in rock property representation were achieved for rock mass deformability, definition of the susceptibility of a rock to bursting failure and the strength of ground that has failed and then been reconsolidated by grout injection. Approaches were developed to reduce the time necessary to construct 3D models and to represent pre-tensioning of reinforcement elements and the placement of trusses in roadway reinforcement designs. These improvements were applied within the numerical codes FLAC, FLAC3D and MAP3D. A practical rock mass classification system was developed using data from exploratory drilling and face mapping incorporating the effects of faulting. Using this rock mass classification and measured gate road deformations, a methodology was developed for the prediction of roadway deformation. Tests with a 3D laser scanner showed the technology was applicable to recording roadway deformation and geotechnical rock mass classification data although use was restricted as it was not intrinsically safe. A practical seismic system was developed to detect geological disturbances up to 50m ahead of an advancing roadway. At the case study site where exploratory drilling ahead of the face was undertaken the seismic results correlated well with the location of water-filled disturbances encountered.