| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 106 === Calcareous sand is formed by biodegradation, composed of calcium carbonate, and weak structurally compared to quartz sand. Calcareous sand has high void ratio and angular particle shape. They can be found in tropical and subtropical shallow waters. It is highly likely that calcareous sand would be encountered in the construction of coastal and offshore structures, such as port facilities, sea base, and offshore wind turbines Hence, it is important to study the behavior of calcareous sand. Determination of the dynamic properties of calcareous sand is the focus of this study.
In this study, resonant column tests were performed to evaluate the small-strain dynamic properties of calcareous sand, which was obtained from the coastal area of Penghu. Reconstituted specimens were prepared by the compaction method. Impact of void ratios, degrees of saturation and confining pressures on dynamic properties were investigated. Correlation relationships to estimate the maximum shear modulus and the minimum damping ratio of Penghu calcareous sand were developed.
A relative density-controlled cyclic triaxial tests were performed on specimens with the same three void ratios as used in the resonant column test. Liquefaction resistance of Penghu calcareous sand with different relative densities were determined.
The test results show that the shear modulus and damping of dry sand are smaller than those of wet sand, while the normalized shear modulus of dry sand is higher than that of wet sand. Separate correlation relationships were developed for dry sand and wet sand to predict Dmin and Gmax.In addition, degree of saturation would not affect Dmin of wet sand. Lastly, it is found that the liquefaction potential of Penghu calcareous sand is significantly lower than that of quartz sand and other in-situ soils.
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