GEOTECHNICAL FEATURES OF THE SEABED SOILS IN THE EAST OF XISHA TROUGH AND THE MECHANICAL PROPERTIES OF GAS HYDRATE-BEARING FINE DEPOSITS
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摘要: 利用2012年在西沙海槽东部海域获得的25个重力柱状样的土工试验分析，以及以南海北部陆坡区浅表层土为试验介质的含水合物细粒土的力学特性模拟试验结果，对西沙海槽东部海域浅表层土的工程地质特性和含水合物细粒土的力学特性进行了综合分析。结果显示西沙海槽东部海域浅表层土土质类型单一，主要为高液限粉土，粉砂含量较高，黏粒含量次之，砂粒含量极少。通过差异显著性检验，陆坡斜坡及北槽坡区与槽底平原和南槽坡区浅层土的工程地质特性差异显著，而垂向上各区浅表层土的工程特性无显著性差异，整体为一高含水率、高塑性、高压缩性和低抗剪强度的软弱高液限粉土层。以细粒土为试验介质，不同水合物饱和度土的土力学特性有较大差异。低饱和度的土表现为两次塑性破坏，而高饱和度的土仅表现为一次塑性破坏。水合物细粒土的黏聚力值随饱和度的增加呈现先增加后降低的趋势，内摩擦角随饱和度的变化不明显。Abstract: In order to define the geotechnical features of the seabed soil and the mechanical properties of the hydrate-bearing fine deposits, soil testing was carried out for the gravity cores recovered from the east of the Xisha trough in 2012 in addition to the mechanical experiments of tetrahydrofuran (THF) hydrate in the fine deposits taking from the northern slope of the South China Sea. Results show that the seabed soil of the investigation area is simply composed of elastic silt (MH). There are significant differences in geotechnical features of the seabed soil among the northern slope of the continent, the northern slope of the trough, the trough plain and the southern slope of the trough. The fine soil with different hydrate saturation is also very different in geotechnical features. The soil with low hydrate saturation has twice of plastic failure, while the soil with high hydrate saturation has only once. As the hydrate saturation increases, the cohesion of hydrate-bearing fine soil increases first, then decreases. However, the angle of internal friction doesn't change distinctly.
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Keywords:
- seabed soil /
- geotechnical features /
- gas hydrate fine soil /
- mechanical experiment /
- Xisha trough
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