| Summary: | 碩士 === 淡江大學 === 土木工程學系碩士班 === 93 === In this study, wave equation is used to model the dynamic responses of the foundation in a liquefied ground due to the earthquake. Based on the bore-hole data and the seismic records, the soil parameter reduction factor can be obtained from the liquefaction potential analysis such as those suggested in the Japanese codes. The reduction factor can be used to reduce the soil stiffness along the pile in the liquefaction zone. Lumped mass analysis is performed to obtain the free-field response of the liquefied ground. The deformations of the ground are then superimposed onto the pile elements for the discrete wave equation analysis. Thus the pile response and the failure mechanism are investigated. Besides the studies on Yuan-Lin County sites with Chi-Chi earthquake record, a number of case studies for 1964 Niigata earthquake are used to validate the proposed procedures.
The main observations of this study are: (1) The ground displacements at the surface would not be amplified by the soil liquefactions, however the ground and the pile displacements are significantly increased in the zone of liquefaction. (2) With or without the liquefaction, a large earthquake would cause excessive moments and shears for the piles near to the head, in which the pile may fail accordingly. (3) Complex failure mechanism could happen according to the connections between the pile and the cap. Further cautions would be required for the foundation structure near by the interfaces of the liquefied and non-liquefied soil layers. (4) The procedures suggested in this study could predict successfully the pile foundation responses in a liquefied ground. It can be used to model effectively for the failure behavior of the pile foundation due to the soil liquefaction.
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