In London Ontario, the combination of water-laid glacial till and the water table sitting just a couple of meters down catches a lot of builders off guard. We see it regularly—soil that looks stable during a dry summer turns into a problem once you factor in seismic shaking. The city sits in a moderate seismic zone, and the National Building Code of Canada (NBCC 2020) requires a liquefaction check for any Site Class D, E, or F profile. Our team runs the analysis directly from raw field data. No generic assumptions. We pull continuous CPT test logs to map the cyclic resistance ratio layer by layer, then cross-check critical zones with SPT drilling to confirm the fines content and plasticity. That combination gives you a defensible factor of safety for your foundation design.
A clean sand with 15% fines can behave entirely differently than the same sand with 30% fines. London's till mixes demand that distinction.
Our approach and scope
Site-specific factors
London's expansion east and south is pushing development onto the glacio-lacustrine deposits from the old Lake Whittlesey shoreline. These silts and fine sands are precisely the materials that can lose all strength for a few critical seconds. We've reviewed borehole logs from the White Oaks area where loose saturated sands sit trapped under a desiccated crust. The risk isn't just bearing failure. Settlement after shaking can crack slabs and sever utilities. The NBCC mandates a site-specific analysis for any building with a post-disaster importance category. Skipping it means the building official will reject the submission. But beyond compliance, it's about real performance. A structure on shallow footings over a liquefied layer can tilt irreversibly. We quantify that tilt so the structural engineer can decide if deep foundations or ground improvement is the right path.
Video resource
Applicable standards
NBCC 2020 (National Building Code of Canada, seismic provisions), CSA A23.3-19 (Design of Concrete Structures, seismic annex), ASTM D6066-11 (Standard Practice for Determining the Normalized Penetration Resistance of Sands), ASTM D5778-20 (Standard Test Method for Electronic Friction Cone and Piezocone Penetration Testing), ASTM D5311/D5311M-13 (Cyclic Triaxial Test for Liquefaction)
Other technical services
Site-Specific Seismic Hazard
We pull the NBCC uniform hazard spectra for London's coordinates and deaggregate to get the controlling magnitude and distance for liquefaction triggering.
CPT-Based Liquefaction Screening
We use the Robertson (2016) CPT method with soil behavior type index correction for London's silty clay layers that can mask as sand.
Post-Shaking Settlement Analysis
We run the Zhang et al. (2002) and Idriss & Boulanger (2008) volumetric strain models to give your structural team the expected ground surface drop.
Typical parameters
Quick answers
What does a liquefaction analysis for a London Ontario site typically cost?
For a standard commercial site with two CPT soundings and cyclic triaxial on two samples, plan on CA$3,400 to CA$6,380. The range depends on depth—a 20-meter profile costs more than a 15-meter one—and whether we need to bring the CPT rig from the GTA. A pre-drilling SPT program adds to the total but gives you the physical samples for index testing.
Does the NBCC require a liquefaction study for my London project?
Yes, if the site class is D, E, or F and the building is not a low-importance farm building. London's typical silty sand profiles often classify as Site Class D or E. The NBCC 2020 Commentary J is explicit—you must prove the factor of safety against liquefaction is at least 1.1. We write the report to satisfy the city's building department reviewer.
How do you handle the stiff clay layers common in London's till?
We use the Robertson soil behavior type index from CPT data to separate clay from sand. The clay is not liquefiable, but it caps pore pressure dissipation. We model that cap in our analysis. For SPT samples, we run Atterberg limits to confirm the PI and liquidity index so there's no ambiguity.