循环荷载下海上风电桩基水平承载特性研究

发布时间：2018-01-04 08:05

本文关键词：循环荷载下海上风电桩基水平承载特性研究　出处：《中国海洋大学》2014年硕士论文　论文类型：学位论文

【摘要】：海上风电作为一种新型清洁能源，在21世纪越来越受到人们的青睐。黄河三角洲作为中国第二大中国石油基地，又具有丰富的海上风能资源，因此在黄河三角洲地区粉质土的地质概况下桩基础的稳定性越来越受到关注。由于桩基础所受荷载的复杂性，以有机玻璃管模拟桩体，在饱和粉质土地基中进行了单桩水平静力和单向循环加载室内模型试验，通过应变采集系统和位移计测得两种设桩方式和加载方式下的桩身应变和桩身位移。并通过数学运算推出静力加载和单向循环加载下单桩的桩身弯矩、桩体位移、桩周土反力等数据。通过分析得到如下成果：（1）水平静力加载下，对于两种不同的设桩方式，随着荷载的增大，桩周土的变形和桩身弯矩都增大。由于桩周土体开始产生塑性屈服，从而对桩的侧向约束能力下降，最大桩身弯矩位置有所下降，始终处于距离泥面3至6倍桩径，而打入桩最大桩身弯矩值较预埋桩大。（2）水平静力加载下，设桩方式对桩周土反力的的主要影响是，通过改变原土体应力状态在深度上的分布，降低了土抗力零点位置，这种效应随着深度的增大而减小，因此对于Y50修正值是随着深度增大呈增大的趋势。（3）通过预埋桩和打入桩在静力加载下推算的p-y曲线发现，对于接近泥面处的桩土综合刚度，打入桩较预埋桩小，这种现象随着深度的增大而减弱。（4）API中软粘土的p-y曲线模型并不适用于粉质土，由于其对极限土抗力的计算偏保守，因此文中Y50相对于文献中的取值较大。（5）单向循环加载下，对于两种设桩方式，通过拟合发现，幅值和峰值应变下最大桩身弯矩之间都呈线性增大关系，而其斜率又与周期的大小相关。因此峰值应变下最大桩身弯矩是与幅值和周期相关的函数。桩身最大弯矩的位置随着幅值的增大向下移动，并一直处于距离泥面4至5倍桩径处。循环荷载的幅值与最大桩周土反力和测点位移之间依然呈正相关，随着幅值的增大，，桩周上部土体变形增大，荷载向更深层的土体传递，因此土抗力零点位置也向下移动。（6）预埋桩和打入桩的单向循环加载下，循环周期对最大弯矩、土反力最大值、测点位移的影响是复杂多变的。（7）对于两种设桩方式，循环次数与峰值应变下桩身最大弯矩、土体位移之间都呈正相关，并通过拟合给出了两种设桩方式下函数中相关参数建议值。其次由于循环弱化作用，循环次数与最大桩周土反力之间呈负相关性，并通过拟合也给出了两种设桩方式下相关参数的取值。（8）由两种设桩方式下动力p-y曲线峰值变化趋势显示，桩周最大土抗力与循环次数之间的关系取决于一个临界深度，在临界深度以上最大桩周土抗力与循环次数呈负相关，而在临界深度下两者呈正相关。
[Abstract]:As a new clean energy, offshore wind power has been more and more popular in 21th century. The Yellow River Delta is China's second largest oil base, and has abundant offshore wind energy resources. Therefore, the stability of pile foundation is paid more and more attention under the geological condition of silty soil in the Yellow River Delta area. Due to the complexity of pile foundation load, the laboratory model tests of single pile under horizontal static and unidirectional cyclic loading were carried out in saturated silty soil foundation by using PMMA pipe to simulate pile body. The strain and displacement of pile body are obtained by strain acquisition system and displacement meter, and the bending moment of pile under static loading and unidirectional cyclic loading is deduced by mathematical calculation. The results are as follows: (1) the displacement of piles, the reaction of soil around piles, and so on. 1) under horizontal static loading, with the increase of load, the deformation of soil around pile and bending moment of pile body increase with the increase of load, and the soil around pile begins to produce plastic yield. As a result, the lateral restraint capacity of the pile is decreased, the position of the maximum bending moment of the pile body is decreased, and the maximum bending moment of the driven pile is larger than that of the embedded pile, which is 3 to 6 times of the diameter of the pile from the mud surface. 2) under horizontal static loading, the main effect of pile setting on soil reaction around pile is to reduce the 00:00 position of soil resistance by changing the distribution of stress state of original soil in depth. This effect decreases with the increase of depth, so the correction value of Y50 increases with the increase of depth. 3) through the p-y curves calculated under static loading, it is found that the pile-soil stiffness near the mud surface is smaller than that of the embedded pile, which weakens with the increase of depth. The p-y curve model of soft clay is not suitable for silty soil. Because the calculation of ultimate soil resistance is conservative, the value of Y50 in this paper is higher than that in the literature. 5) under unidirectional cyclic loading, it is found that the maximum bending moment of pile under peak strain and amplitude increases linearly. Therefore, the maximum pile bending moment under the peak strain is a function related to the amplitude and the period. The position of the maximum bending moment of the pile body moves downward with the increase of the amplitude. It has always been 4 to 5 times the diameter of the mud surface. The amplitude of the cyclic load is still positively correlated with the maximum soil reaction force around the pile and the displacement of the measuring point. With the increase of the amplitude, the deformation of the upper soil around the pile increases and the load is transferred to the deeper soil. Therefore, the position of the earth resistance at 00:00 also moves downward. 6) under the unidirectional cyclic loading of the embedded pile and the driving pile, the influence of the cycle period on the maximum bending moment, the maximum soil reaction force and the displacement of the measuring point is complex and changeable. 7) for the two kinds of pile setting methods, there is a positive correlation between the number of cycles and the maximum bending moment of the pile body and the displacement of the soil under the peak strain. By fitting, the suggested values of the relevant parameters in the function are given. Secondly, due to the weakening of the cycle, the number of cycles is negatively correlated with the maximum soil reaction around the pile. The values of related parameters under two kinds of pile setting methods are also given by fitting. According to the change trend of peak value of dynamic p-y curve under two kinds of pile setting modes, the relationship between the maximum soil resistance around pile and the number of cycles depends on a critical depth. The maximum soil resistance around the pile is negatively correlated with the number of cycles above the critical depth, but it is positively correlated with the soil resistance at the critical depth.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P752

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