Ottawa, Ontario, is the second-fastest-growing city in Canada and has seen a significant population boom in recent years, according to Stats Canada. With its year-over-year increase in population, underlined by the fact that it is the political hub of Canada, has made projects like the EY Centre a critical piece in supporting the city’s growth. More recently, the importance of the Centre as an inherent part of Ottawa’s infrastructure came to light when Kevin McCrann, president of the EY Centre, reached out to Ottawa’s Mayor Jim Watson’s office to see how it could help by offering the space as a potential overflow space for a pop-up-hospital, should it be needed, given the current situation.
Built by Ruiter Construction, the EY Centre is the largest multi-purpose exhibition facility in Eastern Ontario. The EY Centre is utilized for everything from trade and consumer shows to concerts, banquets, and conferences. With 150,000 square feet of undisrupted exhibition space and 11,000 square feet of meeting banquet space, the EY Centre offers a total of 220,000 square feet of versatile space and an overall capacity for 10,000+ persons.
The site for the proposed EY Centre site had a loose to medium dense liquefiable silty sand layer to approximately 4-5m below the existing grade. The water table was also very high, leading to significant liquefaction concerns at the design return period seismic event. There were some concerns over the static settlement of footings as well due to the generally loose nature of the silty sand soil.
Rapid Impact Compaction (RIC) was chosen to densify the soils through the potential liquefiable zone – and all from the existing grade. This innovative approach avoided the costly and time-consuming process of excavating the soils, replacing and re-compacting them in thin lifts, as is traditionally done. It was determined that if that traditional approach were taken, versus utilizing the RIC system, the risk factor would be far too high, given the moisture content of the in-place soils.
The RIC system uses a heavy (7.5 to 9 tonne) weight lifted and dropped on a large metal-mass foot at roughly 40 times per minute, and a pattern of strikes is designed for the site. For this site, the hit points start at 6 m on center in order to densify the soils at depth, which were determined to be liquefiable to depths of 5m below the surface. The site was then bladed, and a second pattern of 3m on center was used to densify the soils even further. Lastly, the third and final pass involved an offset 3m pattern, such that the entire site was hit every 1.5m. The pattern and schedule of hits were set such that a maximum “rest” time could be left between passes to allow the pore pressures to dissipate in this silty sand material. The on-board computer identified some areas of the site that were not reaching the required level of compaction. As a result, after completing the design passes, specific areas were re-hit to bring the compaction up to the levels needed for liquefaction mitigation.
The RIC system used for this project provided a very rapid and cost-effective approach for densifying the soils in place. Effectiveness of the compaction method was confirmed through the use of advanced on-board computers, which measured real-time compaction levels and a detailed elevation survey of the site, which was confirmed up to 8 inches of the site’s overall drop.
Post-installation SPT testing was conducted to confirm the effective mitigation of liquefaction concerns for the site. GeoSolv was also able to verify through this testing that the footings could be designed for 150 kPa SLS on the improved ground.
This project showed the vital role that large structures like this play, not only for a rapidly growing city but also for unforeseen uses like that as practical space in the event of any significant emergency. GeoSolv was proud to be an essential part of this major project.