Our team brings a large hydraulic grab rig and a full bentonite mixing plant to Calgary sites when diaphragm wall design is the right solution. For deep excavations in the Bow River valley, we first run a geotechnical CPT to map soil layers and detect boulders. The grab bites into clay till and gravel, and we monitor trench stability with a slurry level sensor. Calgary's glacial geology means we often encounter interbedded sands and hard till lenses, which demand precise cut-off criteria. Each panel is excavated to bedrock or a competent bearing stratum, typically 12 to 25 meters deep depending on the project footprint.
Diaphragm walls in Calgary's glacial till require careful control of bentonite density and trench stability, especially near the Bow River.
Methodology and scope
In Calgary we see many owners opting for diaphragm walls as permanent basement walls combined with load-bearing elements. A key advantage is the low water ingress achieved through continuous concrete placement under bentonite. We always specify a tremie seal to avoid cold joints, and we design the wall thickness based on bending moments from lateral earth and hydrostatic pressures. The process integrates with deep soil mixing for toe stabilization and with anchor systems when tiebacks are needed to reduce wall thickness. Our design follows CSA A23.3-19 for reinforced concrete and the NBCC 2020 seismic provisions for the region.
Technical reference image — Calgary
Local considerations
A 15-story tower near the Bow River required a diaphragm wall 22 m deep, but the contractor lost trench stability when the bentonite density dropped during a rainstorm. We stepped in to redesign the slurry mix and added a monitoring system for real-time density readings. The lesson: Calgary's variable groundwater levels and the presence of cobbles in the till demand a solid quality control plan from day one. Without it, cave-ins or panel misalignment can delay the project by weeks.
We analyze soil profiles from boreholes and CPT data to recommend wall depth, panel length, and reinforcement layout. Our team checks for obstructions like buried utilities and boulders before finalizing the geometry.
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Structural Design and Detailing
Using finite element software, we calculate bending moments, shear forces, and crack widths under service and ultimate loads. We produce reinforcement schedules and construction drawings that meet CSA A23.3 and local building permit requirements.
Applicable standards
NBCC 2020 – National Building Code of Canada, CSA A23.3-19 – Design of Concrete Structures, ASTM D4380 – Standard Test Method for Density of Bentonite Slurries
Frequently asked questions
What is the typical cost range for diaphragm wall design in Calgary?
For a medium-sized project (wall depth 15–20 m, total length 100 m), design fees range from CA$2.280 to CA$9.400 depending on complexity, number of panels, and required analysis. Contact us for a project-specific quote.
How deep can a diaphragm wall be installed in Calgary's glacial till?
In the Bow River valley, we have installed walls up to 30 m deep. The limiting factor is often the presence of dense till with cobbles, which may require pre-trenching or a larger grab. At greater depths, panel stability depends on careful bentonite control.
Do diaphragm walls require waterproofing in Calgary?
Yes, even with a well-designed wall, minor water ingress can occur through construction joints. We typically specify a waterstop system at panel joints and may recommend a drainage layer behind the wall in high-water-table areas like the Beltline or Mission district.
What is the difference between a diaphragm wall and a secant pile wall?
A diaphragm wall is a continuous concrete wall cast in panels using a grab, while secant piles are interlocking concrete piles. Diaphragm walls offer higher stiffness and better water tightness, making them preferred for deep basements and cut-and-cover tunnels in Calgary.
