Abstract Monopile has been the most widespread foundation type for Offshore Wind Turbines (OWTs) in shallow waters. Caisson (skirted) foundations have also been evaluated in some projects as an economical alternative. While the main concern in design of offshore foundations has been the environmental loads, the recent growth in construction of OWTs in seismic regions with the possibility of soil liquefaction has necessitated evaluation of the impact of earthquake and liquefaction from strong shakings on these structures. Several studies have reported the consequences of soil liquefaction for buildings and onshore structures; However, the effects of liquefaction on offshore foundations have not been sufficiently studied. This paper investigates the use of advanced liquefaction modeling in assessment of the response of monopiles and caissons for offshore wind turbines. The software FLAC3D and the SANISAND constitutive model are used to conduct the nonlinear dynamic analyses for OWTs. Excess pore water pressure during earthquake shaking and earthquake-induced displacements are computed at various points in the soil medium around the considered monopile and caisson foundations. The analyses reveal that SANISAND model is capable of simulating the pore pressure generation in the free-field as observed in a recent centrifuge test. The numerical results also indicate that both monopile and caissons in liquefiable soil deposits experience considerable rotations under the combined action of wind loads and earthquake shaking when liquefaction occurs.

中文翻译：

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可液化土壤中海上风力发电机单桩和沉箱的地震响应

摘要 单桩一直是浅水区海上风力涡轮机（OWT）应用最广泛的基础类型。沉箱（裙边）地基也在一些项目中被评估为一种经济的替代方案。虽然近海地基设计的主要关注点是环境载荷，但最近在可能发生土壤液化的地震地区建造 OWT 的增长，需要评估地震和强烈震动对这些结构造成的液化的影响。一些研究报告了土壤液化对建筑物和陆上结构的影响；然而，液化对海上基础的影响尚未得到充分研究。本文研究了使用先进的液化模型来评估海上风力涡轮机的单桩和沉箱的响应。FLAC3D软件和SANISAND本构模型用于OWT的非线性动力分析。在所考虑的单桩和沉箱基础周围的土壤介质中的各个点处计算地震震动和地震引起的位移期间的超孔隙水压力。分析表明，SANISAND 模型能够模拟在最近的离心机测试中观察到的自由场中孔隙压力的产生。数值结果还表明，在发生液化时，在风荷载和地震晃动的共同作用下，可液化土壤沉积物中的单桩和沉箱都经历了相当大的旋转。FLAC3D软件和SANISAND本构模型用于OWT的非线性动力分析。在所考虑的单桩和沉箱基础周围的土壤介质中的各个点处计算地震震动和地震引起的位移期间的超孔隙水压力。分析表明，SANISAND 模型能够模拟在最近的离心机测试中观察到的自由场中孔隙压力的产生。数值结果还表明，在发生液化时，在风荷载和地震晃动的共同作用下，可液化土壤沉积物中的单桩和沉箱都经历了相当大的旋转。FLAC3D软件和SANISAND本构模型用于OWT的非线性动力分析。在所考虑的单桩和沉箱基础周围的土壤介质中的各个点处计算地震震动和地震引起的位移期间的超孔隙水压力。分析表明，SANISAND 模型能够模拟在最近的离心机测试中观察到的自由场中孔隙压力的产生。数值结果还表明，在发生液化时，在风荷载和地震晃动的共同作用下，可液化土壤沉积物中的单桩和沉箱都经历了相当大的旋转。在所考虑的单桩和沉箱基础周围的土壤介质中的各个点处计算地震震动和地震引起的位移期间的超孔隙水压力。分析表明，SANISAND 模型能够模拟在最近的离心机测试中观察到的自由场中孔隙压力的产生。数值结果还表明，在发生液化时，在风荷载和地震晃动的共同作用下，可液化土壤沉积物中的单桩和沉箱都经历了相当大的旋转。在所考虑的单桩和沉箱基础周围的土壤介质中的各个点处计算地震震动和地震引起的位移期间的超孔隙水压力。分析表明，SANISAND 模型能够模拟在最近的离心机测试中观察到的自由场中孔隙压力的产生。数值结果还表明，在发生液化时，在风荷载和地震晃动的共同作用下，可液化土壤沉积物中的单桩和沉箱都经历了相当大的旋转。