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REMEDIAL MEASURES INCORPORATING JET GROUTING AND MICROPILES FOR THE CONSTRUCTION OF A NEW BACK FLOW PREVENTER
Session: General Geotechnique and Engineering Geology / Géotechnique générale et géologie de l'ingénieur
Naresh Gurpersaud, Geo-Foundations (Canada)
Jim Bruce, Geo-Foundations Contractors Inc. (Canada)
Mark Redden, Geo-Foundations Contractors Inc. (Canada)
A new back flow preventer (BFP) was constructed as part of Toronto’s West Don Lands (WDL) redevelopment in preparation for the 2015 Pan Am Games. Movement of three adjacent existing bridge piers early during conventional construction necessitated an embargo on dewatering, a change from conventional to innovative techniques as well as remedial measures to construct the new backflow preventer. The site is located within the flood plain of the Don River and is underlain by over 30 metres of weak organic deposits. Overlapping jet grouted columns were installed using the double fluid process to create both a low permeability base plug and a vertical cut-off. Rock-socketed micropiles were installed through the jet grout base plug to support and tiedown the new chamber. Several challenges were encountered during remedial works, namely revisions to the method and sequence required to mitigate further movement of the adjacent bridge piers. Eventually additional micropiles were installed as part of a foundation retrofitting scheme to permanently transfer the foundations of the three existing bridge piers to rock. Details of the jet grouting, backflow preventer micropiles and bridge micropiles, including test programs and challenges encountered during construction are outlined in this paper.
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