CONSTRUCTION OF A DEEP SOIL MIXED CUT-OFF AND RETAINING WALL IN RICHMOND BC-Paper

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The River Green Residential development in Richmond, British Columbia, required a temporary groundwater cut-off and retaining wall for construction of an underground parkade beside the Fraser River and Richmond Olympic Oval. Permeable alluvial sands, shallow tide-influenced groundwater, and sensitive neighboring structures made conventional excavation support and dewatering challenging.<br /><br />The design used Cutter Soil Mixing (CSM) to build a continuous, 350 m perimeter wall comprising 139 interlocking soil-cement panels. The wall extended about 28 m below ground and was keyed into marine clay. Its narrow 650 mm footprint and low-vibration construction suited the confined urban site. H-piles reinforced the wall at regular intervals. The upper 13 m was designed to provide both retaining support and seepage control, requiring a 4 MPa unconfined compressive strength (UCS); the lower 15 m served as a cut-off, with a 0.5 MPa UCS requirement. The wall’s hydraulic conductivity target was no more than 1 × 10⁻⁷ cm/s.<br /><br />Laboratory and field trials informed the binder mix and construction procedures. Bentonite slurry improved cutter penetration, while a Portland cement and ground-granulated blast-furnace slag blend provided suitable strength and permeability. Wet-grab and core samples were tested, alongside monitoring of construction parameters and groundwater and vibration levels.<br /><br />The completed work met specifications and finished ahead of schedule. Tested specimens averaged 5.3 MPa UCS and 8.8 × 10⁻⁸ cm/s permeability. Peak particle velocity was below 10 mm/s approximately 2 m from the wall, and monitoring was used to check for groundwater changes near the Olympic Oval.<br /><br />The project demonstrated that CSM can create a robust, low-permeability excavation enclosure with minimal vibration, while allowing different sections of a wall to be tailored to distinct structural and seepage-control requirements. Early contractor involvement in trials and design helped refine quality, cost, and schedule.

Keywords

River Green Residential

Richmond British Columbia

Cutter Soil Mixing

groundwater cutoff wall

retaining wall

underground parkade

Fraser River

alluvial sands

low-vibration excavation

hydraulic conductivity