| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 90 === In this study, the nonplastic sand with high fines content in Maoluo River area of Nantou City was used as test samples. The specimens were prepared by moist tamping to a same dry density for sands with different fines content. Triaxial liquefaction tests were performed with CKC cyclic triaxial test system. The purpose of this research is to investigate the effect of fine content on the liquefaction strength of soils. The test results of soils from Yuanlin and Tsaotun areas were also evaluated for the understanding of the relationship of fines characters and liquefaction strength.
The test results show that liquefaction strength of soils of Maoluo River decrease as the silt content increases until a minimum liquefaction resistance is reached at a silt content of 20%. As the silt content continues to increase above 20%, the liquefaction resistance increases. The liquefaction strength of silt which contains 100% fines is 30% greater than that of sand which contains 0% fines. As silt content is low, the soil can be described as consisting of silt content in a sand matrix and liquefaction strength is controlled by the coarse grain. As silt content is high, the soil can be described as consisting of sand particles in a fines matrix and liquefaction strength is controlled by the fine grain.
As silt content is low, there is a better relationship between liquefaction strength and sand skeleton void ratio. For a high silt content , there is a better relationship between liquefaction strength and interfine void ratio.
The test results also show that there is a strong relationship between liquefaction strength and relative density of the whole soil including sand and silt. Liquefaction strength increases as relative density increases. Therefore; it is feasible to evaluate the liquefaction strength of soil containing high fines content according to its relative density.
The test results of sample of Yuanlin area show that pore water pressure of soil containing more fines content increase more slowly as undergo same shear strain amplitude, and liquefaction strength increase as plastic index of fine grain increase. The test results of sample of Tsaotun area also show that liquefaction strength increases as fines content increases.
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