Vancouver sits on a complex foundation of glacial till, marine silts, and soft deltaic clays that make underground construction particularly demanding. The False Creek flats and much of the downtown core rest on sediments that can exceed 30 meters in depth, with groundwater tables often less than two meters below the surface. Tunneling through these materials requires more than standard investigation. Our laboratory runs constant triaxial and consolidation tests on undisturbed samples to provide the parameters needed for settlement prediction and face stability analysis. For open-face TBMs in these conditions, we combine advanced lab testing with field CPT data to calibrate the soil behavior model before excavation begins. The Fraser River delta adds another layer of complexity, with interbedded sand lenses that can destabilize a tunnel heading without warning.
Soft ground tunneling in Vancouver is a settlement control problem first and a structural design problem second.
