195. PILE BEHAVIOR DUE TO EARTHQUAKE INDUCED LIQUEFACTION AND LATERAL SPREADING IN LARGE SCALE TESTING
Name: Ahmed Amr Ebeido
Grad Year: 2018
Earthquakes cause significant damage and billions of detrimental economic consequences. Liquefaction of soils surrounding pile foundation during earthquakes affects pile response; leading to damage and collapse of foundation and thus the supported structure. We have to consider two stages of response. First is the response of piles during cyclic ground motion and second is the response during subsequent lateral spreading. Case history investigations helped us better understand the response mechanism, however experiments are needed as the observed response is scarce. Four different large scale laminar container shaking table experiments are conducted to investigate pile response, due to the mechanism of liquefaction-induced lateral spreading. Laminar box used was 12 m long, 6 m high and 3.5 m wide. The box was inclined at 2° and subjected to a 2 Hz sinusoidal motion with amplitude ranging from 0.2-0.3g. Configurations include single piles with different stiffness, pile groups and whether an upper dry soil crust layer exists. Recorded data from these experiments are employed to document and track the evolution of lateral loading on the deployed single pile and pile group configuration. Ground and pile lateral displacement as well as excess pore pressure are discussed. In this series of tests, it is observed that some of the highest pile lateral loads occur at the initial stages of lateral deformation, as the soil excess pore pressures approach the limits of liquefaction. Thereafter, as the soil liquefies, shear strength reduction might permit the soil to more easily flow around the piles. As such, lateral ground deformation that continues to accumulate during the shaking process may not always result in significantly larger lateral pile loads. Comparisons between difference setups, gives us an idea on how the pile group increases the system strength, thus reducing loading and accumulated displacement and how a non-liquefiable crust layer causes additional pressures while limiting the system displacements. Results from these experiments can be used to revise current design methodology, modify provisions of analysis methods such as p-y spring approach and prove the early contribution of kinematic loading to the response. One of the main goals is to be able to predict bridge foundation response in an actual free field earthquake scenario. Another major application is predicting the response of water front structures as platforms and piers due to its vulnerability to lateral spreading and devastating effects.
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