Abstract

The wind turbine has become an efficient way for clean energy. For offshore wind turbine in a sandy area, the monopile is a widely used foundation type under proper water depths. During the life time, monopiles are subjected to millions of cyclic loads from winds and waves and scouring around the pile is a common phenomenon, both of which can influence the operation safety of the offshore turbine. To study the coupled effects of cyclic loading and scouring on the horizontally loaded pile, a series of horizontal monotonic and cyclic loading tests on model piles were carried out in sandy soil. The influence of pile diameter, cyclic loading amplitude, and scour depth on the long-term residual accumulated displacements of a monopile is investigated. The test results show that the deformation mode of pile and the dilatancy of sand result in different static responses of the pile. A quantised work is presented to estimate the accumulated residual displacements of the pile, in which the effects of the three factors can be expressed in a united expression. Since the lateral capacity is a crucial parameter for the normalisation in regression analysis, the confirmation of a lateral capacity should be related to the corresponding concern in practical projects.

摘要

风力发电机已成为清洁能源的有效途径。对于风沙地区的海上风电机组，单桩是一种在适当水深下广泛使用的基础类型。在整个生命周期中，单桩要承受数百万次风浪循环荷载，桩身冲刷是一种普遍现象，这些都会影响海上涡轮机的运行安全。为研究循环荷载和冲刷对水平荷载桩的耦合影响，在砂土中对模型桩进行了一系列水平单调和循环荷载试验。研究了桩径、循环加载幅度和冲刷深度对单桩长期残余累积位移的影响。试验结果表明，桩的变形方式和砂的剪胀性导致桩的静力响应不同。提出了一个量化的工作来估计桩的累积残余位移，其中三个因素的影响可以用一个统一的表达式来表示。由于横向能力是回归分析中归一化的关键参数，因此横向能力的确定应与实际项目中的相应关注点相关。