Excavation and Shoring in the Canadian Greater Vancouver Region – Common Practices and Challenging Case Histories-Paper

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The paper reviews the evolution of excavation support in Greater Vancouver and presents three projects illustrating how shoring methods are adapted to local ground and groundwater conditions. Historically, shotcrete facing reinforced with post-tensioned tieback anchors became the region’s standard approach because it is economical and effective in competent granular soils, glacial deposits, and sedimentary rock. Increasingly deep excavations and more challenging sites have prompted wider use of jet grouting, secant systems, and deep mixing, including hybrid designs.<br /><br />The Alberni by Kengo Kuma project used conventional shotcrete and anchors for an excavation reaching 38.4 m (126 m) below adjacent grades—then Vancouver’s deepest. Wall movements were generally below 25 mm, although loose backfill behind existing foundations caused sloughing and required additional measures. The project highlights the importance of investigating ground conditions behind existing walls before excavation.<br /><br />In Richmond, the Atmosphere project used a reinforced Deep Mixing Method cutoff wall for a 10.6 m excavation in compressible deltaic soils with a shallow water table and loose, saturated sands. Anchor installation caused some soil loss and subsidence. Refining drilling procedures and using partially closed backflow preventors substantially reduced material ingress; subsequent wall movements remained stable.<br /><br />At Brentwood in Burnaby, a hybrid system combined shotcrete above the groundwater head with a jet-grout cutoff below it to manage flowing artesian conditions. The excavation was completed successfully and ahead of schedule. An adjacent phase relying mainly on shotcrete experienced water ingress, sloughing, and slower progress.<br /><br />The cases demonstrate that no single shoring system suits every site. Conventional methods remain effective where soils and groundwater permit, while specialized or hybrid systems can control difficult water and soil conditions. Thorough site investigation, close collaboration among engineers and contractors, and sharing experience with newer techniques are essential to safe, efficient construction.

Keywords

excavation support

shoring methods

Greater Vancouver

shotcrete facing

post-tensioned tieback anchors

jet grouting

secant systems

deep mixing method

groundwater conditions

hybrid shoring systems