Resonant Column Testing at Pressures up to 3.5 MPa (500 psi)

High pressure resonant column tests were needed to determine the earthquake response of a deep soil deposit. Typical confining pressures ranged from 413 kPa (60 psi) to 3.5 MPa (500 psi) requiring the modification and recalibration of a conventional Drnevich-type resonant column. Additionally, test procedures and data reduction methods were adapted for atypical behavior observed during subsequent tests. With the new procedures and calibration, tests were performed to validate the changes using Ottawa Sand, and were compared with cyclic triaxial tests conducted on specimens from the same batch of sand, and published predictions of G_max. Finally, the Ottawa sand results and, results from selected in situ samples are presented.