THE PULL-OUT CAPACITY OF MOBILE PLATFORM LEGS FROM SATURATED SILT

Many new types of structures are extensively used in offshore engineering in recent few decades. Such as the mobile platforms, suction caissons, anchors, spudcans, and so on. The capacities of these structures during penetration, operation and remove are crucial issues for engineers. In this paper, the model test and numerical simulation are conducted to estimate the pullout capacity of the mobile platform's leg submerged in saturated silt. The platform's leg is simplified as a square shape with a dimension of 30cm x 30cm, while the buried depths are 1cm, 3cm, 5cm, respectively. The modified Cam-Clay model and finite deformation theory are applied in numerical simulation. We did the short-time pullout in experiment and numerical simulation. The peak pullout force is about 1-4 times larger than the model's weight. The pullout resistance is influenced by the object buried depth, soil property and so on. It is shown that during uplift, the negative pore water pressure under the object provides the main role to the resistance capacity. As the increase of negative pore water pressure and decrease of the soil confining pressure, the soil failure and large deformation happens, then the structure extricates itself from the silt. The numerical result is acceptable to predict the breakout although couldn't simulate the separation of object and soil.