Construction: 2008 – 2009
Owner: City of Edmonton
Client and Shoring Contractor: HC Matcon Inc.
Structural Engineer: Peter Sheffield & Associates, Isherwood Geostructural Engineers
The Whitemud Retaining Wall was built to replace an existing two-tier bin wall system and allow for the widening of Whitemud Drive and Quesnell Bridge, the busiest bridge in Edmonton. The HCM/Isherwood design-build team’s innovative solution was proposed to the City of Edmonton as an alternative to the original tender, which presented several constructability challenges. The alternative design provided a similar final geometry to the original design while providing higher structural integrity, an improved construction schedule, and significant cost-savings. The HCM/Isherwood team delivered a solution when no other party could tender the base design with confidence.
There were two main phases to the project: a temporary tied-back shotcrete wall (used to provide stabilization for a drilling bench), and a permanent retaining wall. Vertical micropiles were used to prevent settlement of the shotcrete face and to serve as layout points for the irregular arch geometry. Tension micropiles were designed to permanently anchor the reinforced soil mass to the underlying dense sands.
A number of challenges faced the team in considering the best way to stabilize the slope. Site access was difficult and lightweight shoring equipment had to be used given the precarious available installation locations and slope stability. Drainage solutions had to be designed, both for temporary use during construction as well as a permanent system.
The final retaining wall, designed in partnership with Peter Sheffield and Associates, comprised of fourteen unique arches anchored in dense sand, allowing loads to be transferred to the concrete piles pivoting between the upper and lower extremes of the arch. The horseshoes are visually striking and call to mind the epithet ‘form follows function’ for utilizing the arch shapes to stabilize the loads from behind.