SURFACE SEDIMENT STRENGTH IN BED-SLOPE OF NORTHERN SOUTH CHINA SEA

With the rapid development of marine exploitation activities, the sediment strength in the bed slope of Northern South China Sea has attracted more and more attention. The vane shear tests and penetration tests are conducted on ship with the sediment samples collected by gravity corer and box corer in the Yingqiong Slope, Shenhu Slope, Dongsha Slope and Taiwan Slope. Sampling results show that the sediments in Dongsha Slope are sandy and the carbonate nodules with the diameter of 22cm are found. Besides, living bivalve is found on the seabed and the organic remains are found 110cm below the seabed in the Shenhu area. The sediment strength results show that the penetration resistance is less than 0.1N and the vane test strength is no more than 10kPa within 20cm below the seabed. Generally, the sediment strength increases with the depth below the seabed. Furthermore, sediment strength stratification is found within 200cm below the seabed, especially in the Taiwan Slope. The sediment strength is low above the interface and increases sharply under the interface. The sediment strength interface is the potential sliding surface.