Vancouver's geology doesn't forgive assumptions. You hit hard till in some blocks and loose fill or marine silts in the next, often with the water table sitting just a couple of meters down. The real challenge isn't just calculating wall deflections—it's knowing which layer actually controls the behavior. Our lab sees core samples from across the Lower Mainland, and the variability even within a single city lot can be surprising. A standard SPT drilling program gives you a first look at the stratigraphy, but designing a safe excavation means matching those field logs with strength parameters measured under controlled conditions. We run the triaxial and consolidation tests that feed into the finite element models so the shoring contractor isn't guessing when they hit a pocket of saturated silt near the Georgia Viaduct or up in the Grandview cut. The city's seismic setting, framed by the Cascadia Subduction Zone, adds another layer: a temporary excavation still needs to handle the 1-in-475-year ground motion without progressive collapse, and that starts with a reliable stiffness profile from lab data.
In Vancouver till, a meter of undercut into the stiff layer can reduce wall moments by 20%—but only if the sample data confirms you actually have continuous till and not an erratic boulder.
