385,000 lineal metres of Wick Drains installed to a maximum treatment depth of 44m
Tsawwassen Commons is a landmark 550,000sf. retail development with a diverse tenant mix and trading area that will service the affluent areas of Tsawwassen, Ladner, South Delta, North Delta and South Richmond, BC. The property is visible to the 7.9 million annual passengers who travel to the Tsawwassen Ferry terminal along Highway 17 in Delta, BC.
The native soil profile consists of a thin surficial topsoil layer underlain by a +/- 3m thickness of silt and clay deposits, underlain by alluvial sand and silty sand ranging from approximately 13m at the west end of the site to 39m at the east end in depth.
A deep deposit of interlayered soft silt and loose sand extends from below the alluvial sand down to the surface of Pleistocene Glaciomarine Soils, which were encountered at depths ranging from approximately 23m to 50m.
Ground Improvement Solution
Deep Wick Drains are considered as artificial vertical drainage paths that help to dissipate excess pore water from the ground. These Wick Drains are typically installed in soft, saturated cohesive soils to enhance and accelerate subsequent preload performance.
The installation of Wick Drains in the proposed building areas will reduce the preloading time. The Wick Drain spacing was adapted to satisfy the preferred preload time (3 months minimum) with Wick Drains installed at depths ranging from 28m to 44m.
Due to the presence of thick sand layers with qc as high as 20MPa, Menard Canada developed a vibratory system to install the wicks in one continuous process.
The vibratory method did not affect the performance of the preload consolidation time.