Lateral bearing capacity and rotation center variation for modified suction caisson in saturated sand

The modified suction caisson (MSC) is a novel type of foundation for offshore wind turbines. Model tests and numerical simulations were conducted on the MSCs in sand to explore the lateral bearing behavior and variations of the rotation center position. Results show that the MSC can effectively increase the lateral bearing capacity and limit rotation compared with the regular suction caisson. For the MSC, the yield envelope slope at the 1/100 scale is equivalent to the slope at the 1/50 scale. Equations for the yield envelopes under different model scales were obtained. The internal compartment diameter and external structure length have a significant influence on the MSC lateral bearing capacity. Optimal dimensions of the MSC to maximize the bearing capacity were obtained: the ratio of the internal compartment diameter to the external structure diameter is greater than 0.4, and the ratio of the external structure length to the internal compartment length is within the range of 0.2 to 0.6. The rotation center of the MSC moves downward along the caisson embedded depth and moves forward in the loading direction with increasing angular rotation. As the angular rotation reaches 0.02 rad, the position of the rotation center tends to be stable.