为研究水泥土复合桩循环受荷特性,开展水平循环荷载下复合桩承载特性模型试验,分析加固前后桩基承载力、桩身弯矩、循环累积变形、循环刚度以及循环弯矩的变化特征,提出适用于水泥土加固桩桩顶循环累积位移预测模型。结果表明,相比未加固桩,加固桩初始刚度和极限承载力均有显著提升,桩身最大弯矩降低,改善了桩基整体受荷性能;无论是否加固桩,桩顶循环累积位移均随着循环次数的增加,初始阶段增长较快,而后逐渐趋于稳定;水泥土加固可有效提高桩基水平刚度,但无法改变随循环荷载幅值增大而衰减的规律;未加固桩循环弯矩存在显著的累积现象,而加固桩循环弯矩值降低的同时累积效应基本可忽略。
Abstract
The monopile foundation of offshore wind turbines is subjected to cyclic loads such as wind, waves and currents for a long time, resulting in excessive cumulative deformation of the pile foundation. The monopile foundation is strengthened in the shallow layer with cement-soil to form a composite pile, so as to achieve the purpose of reducing the cyclic cumulative deformation. To research the cyclic behavior of monopile in cement-improved clay, a series of model tests on the lateral bearing capacity of monopile in cement-improved clay under lateral cyclic loading were carried out. The variation characteristics of monopile bearing capacity, pile bending moment, accumulated deformation, cyclic unloading stiffness and cyclic bending moment before and after reinforcement were analyzed. The test results show that the initial stiffness and ultimate bearing capacity of single pile are significantly strengthened by cement-improved soil, and the maximum bending moment of pile is reduced, which improves the overall load performance of pile. Regardless of the reinforced or the unreinforced pile, with the increase of cycle times, the cumulative displacement of pile top cycle increases rapidly initially, and then gradually stabilizes. Cement-soil reinforcement can effectively improve the horizontal stiffness of pile foundation, but it cannot change the law of attenuation with the increase of circulating load amplitude. There is a significant accumulation of the bending moment of the unreinforced pile, but the cumulative effect of the decrease of the reinforced pile can be ignored.
关键词
海上风力机 /
桩基础 /
水泥土 /
模型试验 /
水平循环荷载
Key words
offshore wind turbines /
monopile foundation /
cement-improved clay /
model test /
cyclic lateral loading
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基金
海岸灾害及防护教育部重点实验室（河海大学）开放基金（202303）
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