Application of scout-hole surveys for rockburst prediction for deep tunneling operations

Natalie Blacklock

In the proceedings of: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: INFRASTRUCTURE - IV Pipelines & Tunnels

ABSTRACT: During deep tunnel excavation in hard rock, strain bursting is an important rockburst mechanism that occurs in the walls and tunnel face. As the tunnel advances, intersections with different lithological units and geologic structures can lead to increased stress concentrations, which can result in strain bursting. Current rockburst prediction techniques neglect key geologic structures in the modelling, which over-predicts the stresses necessary to create rockbursts. The application of scout-hole programs is proposed as a way to improve rockburst prediction ahead of the tunnel advance. Acoustic televiewer, optical televiewer, and mechanical property data was collected from a deep underground mine in Sudbury, as part of a scout-hole program running directly parallel to a planned exploration-ramp. The survey was conducted through mafic norite. Two major geologic structures were identified across acoustic and optical televiewer surveys and generated reductions in mechanical properties. From drill core logging, the structures corresponded to the intersection of a 0.20m thick mafic dyke and a 0.15m thick shear zone. Based on the results of the case study, scout-hole surveys are a useful addition to suite of rockburst prediction techniques.

RÉSUMÉ: Le relâchement soudain des contraintes représente un important mécanisme des coups de terrains affectants les excavations souterraines en roches dures. Au fur et à mesure que le tunnel est excavé, des champs de contraintes complexes sont générés à proximité du front de taille, menant ainsi au éclatement de la roche. La prédiction de coups de terrain négligé différentes composantes géologiques pouvant affecter la nature du stockage sont souvent négligées dans la modélisation, ce qui mène à la sur-prédiction des niveaux de contraintes et donc du potentiel de coup de terrain. Le -coups de terrain au niveau des fronts de taille. furent condde trous-pilotes dans une mine sous-terraine de Sudbury, Ontario. Le relevé a été réalisé dans de norite mafique. Deux tions dans les propriétés mécaniques. -pilote avec t avec une zone de cisaillement trous-t acoustiques, et propriétés mécanique sont donc utiles pour identifier les changements de lithologie.

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