Vertical Bearing Behavior of Monopod Caisson Foundation in Sandy Soils

Abstract

This paper presents the results of numerical investigation on the vertical bearing behavior of monopod caisson foundations embedded in sandy soils and supporting offshore wind turbines. The effects of embedment depth and internal soil plug were investigated. The magnitude of lateral soil deformation at the foundation tip is noted to increase with skirt length and it remains greater in comparison with that of an embedded solid foundation. The internal soil plug is found to have a cushioning effect during the transfer of superstructure load to the soil mass underneath the foundation tip. This leads to a reduction in the end-bearing component of vertical capacity when compared with that of an embedded solid foundation. The failure of the soil at the tip resembles the shape of an inverted parabola in the case of caisson foundation and that of an upright parabola for the embedded solid foundation. Based on the results, predictive expressions have been proposed to determine the ultimate vertical bearing capacity of the caisson foundation and its settlement for the range of geometry and superstructure load considered in the study.