Evaluation of the seismic response of gentle slopes in soft clay

Abstract

This thesis examines the seismic response of gentle slopes in soft clay through centrifuge experiments and numerical modeling. A series of centrifuge tests considering slope angles of 3 and 6 degrees was performed on kaolin clay models. A model preparation methodology was developed to simulate uniform soil profiles and to consider the presence of a soft weak layer. The centrifuge experiments were carried out at the Schofield Centre, University of Cambridge, using models tested at an acceleration of 60g, and the earthquake ground motions were applied with a shaking table. In-flight characterization of the undrained shear strength and shear wave velocities was achieved by means of T-bar and air hammer tests. The centrifuge models were subjected to a series of input motions with different amplitudes and frequency content, and the response was monitored using accelerometers, pore pressure sensors and displacement transducers. Complementary data were obtained using particle image velocimetry (PIV). The centrifuge test data were utilized to calibrate numerical models in the software OpenSees using three-dimensional soil columns and a dynamic nonlinear constitutive model. Finally, a series of numerical simulations was performed to evaluate the seismic response of submarine slopes representative of the offshore Campos Basin in southeastern Brazil. The influences of slope inclination and depth to bedrock were addressed to provide insight into the performance of submarine slopes under various seismic events typical of intraplate areas.