冲刷作用下两种不同直径的单桩基础循环加载特性?

海上风电大直径单桩基础长期承受来自环境效应的循环荷载以及海床的冲刷作用，冲刷条件下的水平受荷单桩的循环加载特性是海上风电桩基础设计关注的内容。开展了砂土中大直径和小直径单桩基础冲刷条件下长期循环加载的模型试验，探讨了冲刷深度和循环加载幅值对两种基础形式长期承载变形特性的影响。试验研究表明：砂土中循环加载提高了循环后的单桩承载力，其中小直径桩循环后的水平承载力提高更为显著。冲刷导致循环后的单桩承载力下降，随着冲刷深度增加该效果越明显。在循环加载初期，小直径桩残余累积变形的增加速度小于大直径桩。循环次数大于1 000次冲刷深度为2倍桩径条件下，小直径桩的累积变形趋于稳定，大直径桩的累积变形仍继续发展。通过在无量纲循环加载幅值参数中引入冲刷深度对承载力的影响，建立了冲刷条件下两种不同直径桩基的水平循环累积位移计算模型，适用于考虑冲刷影响的单桩长期水平循环累积变形预测。

Comparison of Cyclic Loading Behavior of Two Piles with Different Dimeters under Scouring

The monopile for offshore wind turbine sustains long-term cyclic load due to environment and scouring in the seabed. The long-term cyclic loading behavior of the pile foundation under scouring is an important problem in the design of monopile for an offshore wind turbine. Laboratory model tests were conducted to investigate the performance of a large diameter pile and a small diameter pile in sand subjected to scouring and long term lateral cyclic loadings, in which the influence of scour depth and cyclic loading amplitude on the long-term behavior of the two foundations was discussed. The test results show that the applied cyclic loading improves the post-cyclic capacity of single pile, especially for the small diameter pile. Scour leads to the reduction of post-cyclic capacity of single pile, the effect of which increases with the scour depth. Comparing with the large diameter pile, the increment of residual cumulative deformation of the small diameter pile is smaller in early cyclic loading stage. When the cycle number is larger than 1000 and the scouring depth is twice of the pile diameter, the development of the cumulative deformation of the small diameter pile approaches to be stable, while a further development of deformation appears in the large diameter pile. By bringing the scour affected capacity into the dimensionless cyclic loading amplitude parameters, the lateral cyclic cumulative displacement calculation model of the two kinds of piles under scouring is established, which is applicable to the prediction of long-term lateral cyclic cumulative deformation of single pile considering scouring.