| Summary: | 碩士 === 中原大學 === 土木工程研究所 === 97 === Secondary compression is the rearrangement of sand particles with time under a constant effective stress. This soil behavior also called creep. Laboratory measurements of dynamic shear modulus after primary consolidation in sands show an increase with time. A reasonable mechanism for this time-effect in sands is a continued rearrangement of sand particle during secondary compression. Improved frictional resistance to deformation develops with time with a gradual increase in interlocking of particle surface roughness. The past researches indicated the sand included mica minerals in West-Central Taiwan. These researches almost focused on measurement of compression index in micaceous sand, ignoring the secondary compression index.
This study used Mia-Liao sand、Ottawa sand to mix with muscovite and sericite at different percentages to make oedometer specimens. In addition, known percentages of Ottawa sand and muscovite were used to perform the XRD test, and the results were used to get a β value by linear regression. The results show that the higher the mica content, the higher the initial void ratio, and the higher the compression index. Compression index and secondary compression index of the mixtures of Mai-Liao sand and mica almost increase with consolidation pressure. But, there is a situation of rising first then drop for compression index and secondary compression index of the mixtures of Ottawa Sand and mica. The ratio of Cα/Cc decrease with increasing in mica content. The lowest value even less than 0.01 . The results of XRD show that there is a β value of 1.736 by regression, and use the β value to estimate the mica content to be 8% to 12% for Mia-Liao sand.
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