| Summary: | 碩士 === 國立高雄第一科技大學 === 營建工程研究所 === 101 === Experiences learnt from earthquake-induced liquefaction disasters in Taiwan and other countries show us the importance of taking it into consideration as making a design. When loose saturated sandy soils were excited by seismic waves, it would induce the rise of the excess pore water pressure and reduce the contact force between the sand particles, and then soil liquefaction occurred. When the building situated on liquefiable soil, once soil liquefaction occurred, bearing capacity of structure would decrease significantly and then settlement of the structure took place.
In this study, a dynamic centrifuge test and numerical simulation were conducted to evaluate the effect of shallow foundation sitting on liquefiable soils after seismic response. Shallow foundation sitting on saturated and unsaturated soils improved by air injection method were implemented in the centrifuge test in Ehime University, Japan by the author. The numerical simulation of centrifuge model test is carried out by the use of a three-dimensional effective stress finite element analysis and a two dimensional finite element method used by practical engineers, to validate the numerical codes and parameters. Finally, this thesis discussed and improved a simple evaluation method proposed by Chang (2011) on predicting the settlement of shallow foundation on liquefied soils. The results showed that the use of air injection technique was able to desaturate the saturated soils, and increase its resistance to liquefaction. The predicted settlement of the shallow foundation showed good agreement to a little conservatism to the collected data from the references. This showed the feasibility of this evaluation method, and hopefully the theory is able to be used in geotechnical practices.
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