| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 93 === There are two types of tests carried out in this study. One is the cyclic traixial test, another is the large scale shear box test on the shaking table. In the traixial test, we prepared the sand specimen with relative density of 51% and 82% by dry pluviation. We continued the cyclic loading on the satured specimen after initial liquefaction until the given axial strain limit to observe the shear strain, the pore water pressure and the reconsolidation volumetric strain. In the shaking table test, the soil sample deformed according to the shear waves induced from the shaking table motions. We prepared the sand specimen by the wet sendimention method. We input acceleration amplitudes from 0.03 g to 0.15 g, frequence of 1 Hz, 2 Hz, 4 Hz and 8
Hz and duration of 5 sec, 10 sec, 20 sec and 30 sec.
In the cyclic traixial test, we find the reconsolidation volumetric strain is related to the necking length on the upper part of the specimen after initial
liquefaction of denser specimens. But for the looser specimens, because the reduction of diameter occured in the whole specimen length, the necking length of loose specimen becomes unmeaningful. In the shaking table test, the increase of shear strain amplitude with time after initial liquefaction implies the sand specimen softened further. At the interface between liqufied and non-liquefied soil layers, we find that the shear strain decrease with time after initial liquefaction resulting from the drainge which leads to the soil stiffness recovery. We also find the interface between the liqufied and non-liquefied soil layer will gradually shift upward. In the multi-directional shaking table test, when the combined shear strain decreases with time, the pore water pressure reduces slower than that in the single directional shaking table test. We also find the maximum shear strain after initial liquefaction during vibration have no obvious relationship with the re-consolidation volumetric
strain.
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