Thinking Bigger â€“ 32-storey Building on Helical Piles-PPT Presentation

PPT Presentation

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EBS Geostructural Inc. installed helical piles for a 32-storey building on Richmond Street in downtown London, Ontario. The busy urban site, nearby businesses and pedestrian access, and a water table about 10 feet below grade made conventional caissons and driven piles challenging because of their equipment, noise, vibration, spoil handling, and logistics.<br /><br />Eight boreholes identified fill and sand near the surface, followed by clay and dense sand and gravel roughly 45–50 feet below grade. The foundation used 2.25-inch solid steel square-shaft piles with 6-, 8-, and 10-inch helices. Grout was installed along the shafts. Testing included three compression tests and one tension test; a displacement cone used on the first test pile appeared to hang up in the dense layer and was not used again.<br /><br />Design loads were 1,065 kN in compression and 385 kN in tension. The reported ultimate geotechnical resistances were 1,510 kN and 770 kN, respectively. The project installed 543 piles: 467 compression-only and 76 designed for compression and tension. Installation took 42 days, averaging 13 piles per day, with 17,593 feet of pile installed and 12,491 gallons of grout used.<br /><br />The helical-pile option was projected to save about $2 million in foundation costs; load testing reportedly saved a further $500,000. Testing, design, and production took place over an eight-month period in 2018, demonstrating the use of helical piles for a high-rise foundation in a constrained downtown setting.

Keywords

helical piles

high-rise foundation

downtown London Ontario

geotechnical engineering

load testing

grouted shafts

urban construction

compression and tension loads

square-shaft piles

foundation cost savings