Osterberg Memorial Lecture: Application of Seismic Piezocone Soundings to Bi-Directional Load Test Response-Video

Video Transcription

Video Summary

The speaker explained how bi-directional Osterberg cell (O-cell) tests can measure drilled-shaft resistance, including multi-stage tests that substantially increase testable loads. For mid-level cell placement, he argued that widely spaced SPT N-values are too crude and recommended seismic piezocone testing (SCPTU), which provides continuous measurements of cone resistance, sleeve friction, pore pressure, and shear-wave velocity. These data support more reliable estimates of shaft and base resistance and help optimize cell elevation. Case studies from Atlanta, Calgary, Charleston, and Vancouver showed generally good agreement between predictions based on SCPTU data and measured O-cell test results. In the discussion, he explained that negative pore pressures can occur in fissured, heavily overconsolidated soils because of dilation and suction. He also noted that O-cell testing can justify more efficient foundation designs, and that cones can penetrate some very hard, weathered materials when suitable equipment is used.

Keywords

O-cell testing

drilled-shaft resistance

SCPTU

cone resistance

pore pressure

foundation design