A cone penetration test (CPT) rig advancing through the soft deltaic deposits of Richmond or Delta reveals more than just stratigraphy — it uncovers the liquefaction susceptibility that defines geotechnical design in Vancouver. Our team deploys seismic CPT (SCPTu) equipment capable of recording pore pressure dissipation and shear wave velocity in a single push, a methodology that has become standard practice for projects east of the Coast Mountains. We correlate the normalized tip resistance and friction ratio with the cyclic resistance ratio (CRR) using the updated Boulanger & Idriss (2014) framework, rather than relying on older SPT-based charts that tend to overestimate resistance in the fine-grained sands of the Fraser River floodplain. In our experience, the local geology demands this level of precision — interbedded silts and clean sands respond very differently to cyclic loading, and a mischaracterized layer can compromise an entire foundation design. When site conditions require supplementary data, we pair the CPT program with MASW surveys to determine VS30 for site classification, and in coarser deposits we use SPT drilling to recover disturbed samples for grain-size verification, ensuring the fines content correction is grounded in physical evidence rather than assumed correlations.
Liquefaction in Vancouver's deltaic soils is not a binary 'yes or no' — it demands a probabilistic assessment that accounts for the full earthquake magnitude, distance, and site-specific ground motion amplification.
