Development of an earthquake motion simulator for centrifuge testing and the dynamic response of a model sand embankment

For embankments constructed with zones of saturated and cohesionless soil, the phenomenon called liquefaction is a potential cause of failure. In order to study the influence that earthquake-induced liquefaction has on embankment response, engineers have relied on observations from rare embankment failures, laboratory tests of soil elements, and theoretical studies. Recently the geotechnical centrifuge has been used in physical modeling experiments to study the liquefaction of embankments during earthquakes. It is now recognized as an important tool for such work.;Centrifuge model studies of embankment response during earthquakes are linked to the capability to simulate the excitation of earthquakes, and various efforts have been made to develop such capabilities for existing centrifuges. This study included the development of an electrohydraulic earthquake motion simulator for a 15 g-ton centrifuge. The development included the design of the simulator, the application of a correction algorithm for achieving scaled earthquake motions, and the characterization of the response of the simulator and the response of the centrifuge arm and basket to the simulator motions.;The development of the earthquake motion simulator represents a successful application of hydraulic control system technology for centrifuge applications. The response of the centrifuge arm and basket to the earthquake motion simulator excitation was characterized by low and high frequency resonance phenomena.;The study further included experiments conducted on a model embankment comprised of loose, water-saturated sand. The embankment experiments were ambient vibration and earthquake base-excitation experiments. The objectives of the experiments were the identification of the fundamental shear mode of the model embankment from the low level test data, and the measurement of the failure response of a model embankment for which a contractive response would result from the earthquake excitation.;The low level response of the model sand embankment was dominated by a fundamental shear response mode consistent with measurements of full scale embankment response. The response of the embankment to a simulated earthquake was a contractive response characterized by rapid buildup of excess pore pressure immediately following the first shock of the base excitation, and corresponding loss of shearing resistance. The embankment failed by lateral spreading.