Evaluation of seismic site response of submarine clay canyon : centrifuge modeling

Abstract

Morphological features of submarine canyons significantly modify the amplitude, duration and frequency content of free-field seismic ground motions. This thesis examines the influence of these morphological features through a series of seismic centrifuge tests on kaolin clay models with canyon sloping angles of 15°, 30° and 45°. These tests were performed in the IFSTTAR geotechnical beam centrifuge, in France, under an acceleration of 40g by applying, trough an embarqued shaking-table, a set of dynamic excitations, varying the amplitude and the frequency content. The response of the clay canyon models was monitored by means of accelerometers and pore pressure transducers. In-flight characterization was performed on each clay model with bender element and T-bar penetration tests prior to the application of seismic excitations. The present research proves that the topographic shape of the canyon can substantially affect peak values and the frequency content of the free-field motions along the slope surface. The low intensity seismic excitations and frequency content along with the dominant frequency of the soil deposit can cause substantial amplification. In addition, higher intensity motions tend to move away from the fundamental site period due to reduction in the shear modulus and increased damping caused by increasing shaking intensities.