Abstract

Suction-bucket-supported jacket foundations are being used increasingly for offshore wind turbines, the advantages being large bearing capacity and efficient installation. For a large-capacity wind turbine, the pullout capacity and displacement of the bucket in the tripod or tetrapod jacket can be critical to the safety of the structure. The loading rate, which is commonly dominated by the offshore environmental conditions, has a significant effect on the ultimate capacity and stiffness of the bucket foundation. In this paper, a numerical model is developed to investigate the response of a bucket foundation under vertical pullout loading at different rates. A bounding-surface model based on critical state soil mechanics is introduced to account for the soil behaviour under different stress states and drainage conditions. The model is modified and calibrated against a comprehensive set of laboratory tests, including both triaxial compression, triaxial extension and direct simple shear tests in drained and undrained conditions. How partial drainage affects the load–displacement response and pore pressure field are thus presented. A parametric study on the selection of soil parameters is also conducted to shed light on practical foundation design.

摘要

吸水桶支撑的导管架基础越来越多地用于海上风力涡轮机，其优点是承载能力大，安装效率高。对于大容量风力涡轮机，三脚架或四脚架夹套中铲斗的拉出能力和位移对结构的安全性至关重要。加载速率通常受海上环境条件支配，对斗式基础的极限承载力和刚度有显着影响。在本文中，开发了一个数值模型来研究桶形基础在不同速率的垂直拉拔载荷下的响应。引入基于临界状态土壤力学的边界表面模型来解释不同应力状态和排水条件下的土壤行为。该模型根据一整套实验室测试进行了修改和校准，包括排水和不排水条件下的三轴压缩、三轴拉伸和直接简单剪切测试。因此，部分排水如何影响荷载-位移响应和孔隙压力场。还对土壤参数的选择进行了参数研究，以阐明实际的基础设计。