Drilled Shaft O-Cell Response at Golden Ears Bridge from Seismic Piezocone Tests

The response of deep foundations under vertical loading is classically evaluated using a combination of limit plasticity and static equilibrium solutions for bearing capacity and elastic continuum solutions for displacements. Here, in-situ geotechnical test data are first processed to provide determinations of soil engineering parameters (γt, OCR, σp' Ko, su, φ', E, v) that are then input into the theoretical equations. Alternatively, the foundations can be assessed via direct methods, whereby the results of in-situ tests are scaled to produce response curves. A review of direct methods and several indirect CPT interpretations is presented using a case study from the response of a large deep drilled shaft at the newly constructed Golden Ears Bridge over the Fraser River in Vancouver, British Columbia, which was subjected to a staged Osterberg load testing sequence. Interpreted geotechnical parameters are obtained from a 100-m deep seismic piezocone sounding that provided four separate readings with depth (qt, fs, u2, and Vs).