Abstract: Bucket foundations are widely used in ocean engineering. The determination of the penetration resistance is a key to the successful application of this type of foundation. In ocean engineering, the properties of silt is largely different from sand and clay. But the existing calculation method of penetration resistance of bucket foundation is generally for sandy soil, which neglects the influence of the cohesion c on the penetration resistance. In this paper, three bucket foundations with different types of tip are penetrated by dead-weight and suction pressure. The relations between penetration resistance and penetration depth are measured in the different penetration stages by dead-weight and by suction. Two methods for calculating the penetration resistance of bucket foundation in silt were derived. The effect of drag reduction in different tips were analyzed. Studies have shown that the calculation value of the penetration resistance of bucket foundation by specification in slit is 20% smaller than measured value. Two methods proposed in this paper that can not only accurately calculate the penetration resistance, but also can reflect the drag reduction effect caused by suction. The sharp-tip can reduce the half of the tip resistance and the anti-drag ring reduce the half friction resistance. However, the anti-drag ring will destroy the soil around the wall and formed a seepage channel, which fail to provide the penetration force.

Key words: bucket foundation, silt, penetration resistance, calculation method, anti-drag ring