GEOTECHNICAL FEATURES OF THE SEABED SOILS IN THE EAST OF XISHA TROUGH AND THE MECHANICAL PROPERTIES OF GAS HYDRATE-BEARING FINE DEPOSITS

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.