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 (γ_t, OCR, σ_p' K_o, s_u, 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 (q_t, f_s, u₂, and V_s).