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Title: Effects of earthquake-induced liquefaction on pile foundations in sloping ground
Author: Haigh, S. K.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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This thesis details the results of an investigation into the behaviour of slopes of liquefiable sand under earthquake loading and the influence of these laterally spreading slopes on inclusions such as pile foundations passing through them. A study of the behaviour of these slopes has been carried out using the techniques of dynamic centrifuge modelling. Eight tests were carried out on laterally spreading slopes and a further five on slopes containing instrumented pile foundations. Each model was subjected to a sinusoidal input motion using a Stored Angular Momentum earthquake actuator, causing liquefaction of the sand and lateral spreading of the slope. Data from instruments measuring acceleration, fluid pressure, total stress and bending moment were logged during the earthquake and analysed to reveal information relating to the performance of these slopes during earthquakes. The experiments highlighted the importance of the dilation of liquefied soil to the behaviour of liquefiable slopes. Slope movements were limited by dilation during each cycle of the earthquake which prevented significant soil flow velocities from building up and large pressures were applied to piles from the liquefied soil owing to dilation of soil close to the pile foundation. It was shown that these large lateral forces were not wholly transmitted into bending moments due to the dynamic response of the piles, but this could be the cause of significant pile damage in other situations. It was also seen that present design methods are non-conservative for both the induced bending moments and the applied lateral loads. Further research is needed to develop better design guidance for this situation. The data from these experiments was compared with the results of a number of numerical models constructed during this work in order to simplify the prediction of the behaviour of these slopes. The displacements of the slopes were compared with those predicted using a Newmarkian sliding block approach modified to include the effects of excess pore pressures. This was shown to give reasonable agreement with centrifuge data, though it requires input of a measured or predicted time-history of excess pore pressure to calculate threshold accelerations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available