| Summary: | 博士 === 國立中央大學 === 土木工程研究所 === 91 === With a series of model tests and numerical analysis, pile behavior under sustained axial load are investigated to comprehend with the affections of soil creep on pile load distribution, load transfer and settlement.
From the interface direct-shear test, it is revealed that the displacement rate is proportional to the stress level of the spacemen. As loading time elapsed, the logarithm of displacement rate decreases linearly with the logarithm of time. The slope of this relationship is essentially independent of the normal stress and stress level. Under identical stress level, different soil presents different displacement rate, but the relationships between the logarithm displacement rate and the logarithm of time are similar. From both in-situ and model pile tests, the incremental head settlement and tip load under sustained axial load are discovered, which shows that loading is transferred gradually from shallow to deeper layers. Furthermore, it is revealed from the model pile tests that skin friction decreases in the upper part and increases in the lower part of pile which forming a more uniform distribution of skin friction.
With correspondence principle, a simplified time-dependent pile behavior analysis program is established utilizing viscoelastic—perfect plastic t—z curve. The situations of multiple layers and soil strength increasing with depth are taken into account in this program. Comparing with FEM program and pile test results, this program can rationally simulate the pile behavior under sustained axial load.
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