海洋循环荷载对吸力桶基础水平承载力的影响研究

海上风电吸力桶基础在25年服役期内,海洋循环荷载作用下桩土相互作用与桩周土状态改变,导致其水平承载力改变。为了研究循环荷载对吸力桶基础水平承载力的影响,该文在砂土地基开展模型试验,介绍吸力桶基础和地基建模方法以及砂土地基的制备和测试。根据水平极限承载力试验结果和循环荷载参数设计循环加载试验,得到吸力桶基础的累积转角随循环次数的增加而增加,增速随之降低。通过对循环加载后的吸力桶基础开展水平单调加载试验,并与水平极限承载力对比。结果表明:循环荷载作用下桩周土趋于致密化,从而导致砂土地基中吸力桶基础的水平承载力增加;水平承载力随循环荷载幅值比和循环次数的增加而分别呈线性和指数增加,随循环荷载对称比的增加呈线性减小,并给出相应的归一化计算公式,为吸力桶基础工程设计提供不同循环荷载作用后的水平承载力计算方法。

STUDY ON EFFECTS OF CYCLIC LOADING ON LATERAL CAPACITY OF SUCTION BUCKET FOUNDATIONS

The soil-structure interaction and soil state around the foundation are changed because of long-term cyclic loading during the25-year service period for offshore wind turbines,then resulting in the change of lateral capacity of suction bucket foundations. Physical modelling is conducted on this study in order to study the influence of cyclic loads on the lateral capacity of suction bucket foundations in sand,and the modelling methods and CPT tests results are also provided. The cyclic tests are carried out according to the results of lateral ultimate capacity by monotonic tests and cyclic parameters. The post-cyclic monotonic tests are conducted on the suction bucket foundations after cyclic loads,comparing with the lateral ultimate capacity. The results show that the soil state around the foundation tends to be densified after cyclic loading,which leads to the increase of the lateral capacity of the suction bucket foundations in sand.The lateral capacity increases linearly and exponentially with the increase of the cyclic load amplitude and the number of cycles,and decreases linearly with the increase of the cyclic load symmetry,all the normalization formulas are also given. This paper provides a method for calculating the lateral capacity of suction bucket foundations under different cyclic loads.