Abstract
The scour protection layers are usually installed around the monopiles to prevent the formation of scour hole. While extensive studies have been performed on the effectiveness of scour protection layer as mitigation measure, no study to date has been found to quantify the influence of scour protection layer on the lateral response of monopiles. In this study, centrifuge tests and numerical analyses were performed to examine explicitly the influence of the scour protection layer on the monopile response under lateral load in sand. It was found that a scour protection layer with a diameter of 5 times the diameter of the monopile (5D) and equivalent surcharge pressure of 15 kPa can increase the foundation lateral capacity by more than 30% and significantly decrease the accumulation of deflection by more than 100% in dense sand. Numerical analyses suggested that the beneficial contribution is attributed to the densification of sand and the increase of effective stress around the pile, which increased the stiffness and ultimate resistance of the soil reaction curve (i.e., p-y curve). Numerical parametric studies suggested that the beneficial effect of scour protection layer is also applicable to monopile in loose sand and by considering the contribution of the scour protection layer, the embedment length of the monopile can be reduced by 10%.
Highlights
Monopiles with an aspect ratio (L/D, where L is embedded length and D is pile diameter) less than 6 are the most widely used foundation type for offshore wind turbines
While extensive studies have been performed on the effectiveness of scour protection layer as mitigation mea sure, no study to date has been found to quantify the influence of scour protection layer on the lateral response of monopiles
Numerical parametric studies suggested that the beneficial effect of scour protection layer is applicable to monopile in loose sand and by considering the contribution of the scour protection layer, the embedment length of the monopile can be reduced by 10%
Summary
Monopiles with an aspect ratio (L/D, where L is embedded length and D is pile diameter) less than 6 are the most widely used foundation type for offshore wind turbines. The scour erosion will reduce the foundation embedment and effective stress along the pile, compromising the lateral response of monopile (Lin et al, 2010, 2014; Qi et al, 2016; Li et al, 2020). No research to date is performed to quantify the influence of scour protection layer on the lateral response of monopile. A series of centrifuge tests were carried out first in dense sand to quantify the effect of scour protection layer on the monotonic and cyclic lateral response of the monopile. Numerical analyses calibrated using the centrifuge test data were performed to reveal the mechanisms and provide additional insights
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