Sand deformation behavior around modified suction caissons during lateral loading and analytical method obtaining lateral bearing capacity

The modified suction caisson (MSC) is an innovative offshore wind turbine foundation. Model tests and numerical simulations were carried out to explore the sand deformation behavior around the MSC under lateral loading. The vertical displacements fitting method and the level bubble method were proposed obtaining the sand deformation range. Influences of the vertical load, loading eccentricity and external structure sizes were investigated. It was found that the shape of the sand surface deformation range in front of the caisson can be fitted by ellipse functions. In the limit state, the sand surface deformation ranges around both the MSC and the regular suction caisson (RSC) decrease with increasing loading eccentricity and vertical load. Besides, the sand surface deformation range in front of the MSC increases with increasing the external structure height. Threedimensional shape of the sand deformation range in front of the MSC is dominated by the external structure height and the rotation center embedded depth. Based on the three-dimensional sand deformation behavior and limit equilibrium method, equations estimating the lateral bearing capacity of the MSC were proposed. The bearing capacities of MSCs obtained by using the proposed equations agree well with the test and numerical simulation results.