Performance analysis of deep excavations in rock

Thomas Lardner, K.Y. Lo, Brian Isherwood

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Engineering Geology and Rock Mechanics

ABSTRACT: e analysis of deep excavations in rock Thomas Lardner & K.Y. Lo Geotechnical Research Centre, Western University, London, Ontario, Canada Brian Isherwood Isherwood Associates, Mississauga, Ontario, Canada ABSTRACT This paper analyzes the results from two recent excavations in the Georgian Bay Formation in downtown Toronto using numerical methods. Monitoring results from both excavations indicate that rock mass deformations can be in excess of 20 mm, depending on the orientation in relation to the rock stress direction. Analyses of the excavation behavior indicates that the in-situ stresses in the Georgian Bay Formation at these sites may range between 1.8 and 4.0 MPa. These results are compared with previous results from Scotia Plaza in an attempt to estimate more realistic engineering properties of the Georgian Bay Formation in downtown Toronto for future projects. Ce document analyse à l'aide de méthodes numériques les résultats de deux récentes excavations en centre-ville de Toronto dans la formation de la baie Georgienne. Les résultats de suivi des 2 excavations montrent que les déformations de la masse rocheuse peuvent excéder 20mm, en fonction de l'orientationpar rapport à la direction de contrainte de la roche. Les analyses du comportement d'excavation indiquent que les contraintes in-situ de ces sites dans la formation de la Baie Georgienne peuvent être comprises entre 1,8 et 4,0 MPa. Ces résultats sont comparés avec les résultats obtenus précédemment à la Scotia Plaza dans l'objectif d'estimer des propriétés mécaniques plus réalistes de la formation de la Baie Georgienne pour les futures projets en centre-ville de Toronto. 1 INTRODUCTION The City of Toronto is one of the most developed urban locations in North America. As private development and public infrastructure continue in Toronto, requirements for design and construction of deep excavations in the Georgian Bay Formation will become more demanding. This paper studies two recent projects completed in the Georgian Bay Formation and analyzes the results using numerical methods. The locations of the projects are shown in Figure 1. The excavation of the entry shaft for the Billy Bishop Pedestrian Tunnel, leading to the island airport, was 35 m deep, with 26 m below the rock surface and located adjacent to Lake Ontario. The inclinometer monitoring results are used in conjunction with results of laboratory tests to study the rock mass behavior and relevant engineering parameters. The excavation for a 66 storey condominium/hotel, Living Shangri-La, located at Adelaide Street and University Avenue, consisted of a 26.5 m cut, with 13 m into the rock, and was located in close proximity to the TTC University Subway line. In order to monitor the deformation induced onto the subway structure to ensure they were within allowable limits, inclinometers along the adjacent shoring wall were installed. The results of both analyses are compared with observed rock mass behavior and to the published literature on the Scotia Plaza excavation (Trow and Lo 1989). Figure 1. Project locations in downtown Toronto: 1) Billy Bishop Pedestrian Tunnel; 2) Living Shangri-La, 3) Scotia Plaza 2 BILLY BISHOP PEDESTRIAN TUNNEL The purpose of the Billy Bishop Pedestrian Tunnel project, located in Toronto, Ontario, is to allow for more efficient pedestrian access to the growing Billy Bishop Airport located on Toronto Island. The site location is

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Thomas Lardner; K.Y. Lo; Brian Isherwood (2014) Performance analysis of deep excavations in rock in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper393,author = Thomas Lardner; K.Y. Lo; Brian Isherwood,title = Performance analysis of deep excavations in rock,year = 2014}