砂土中海上风电超大直径钢管桩桩土相互作用研究

发布时间：2018-05-01 12:31

本文选题：超大直径 + 钢管桩　；参考：《天津大学》2014年硕士论文

【摘要】：单桩基础在海上风电场中的使用率占65%以上,是海上风机的主要基础型式。近年来,随着风机单机容量增大及建设水深增加,海上风电单桩基础普遍采用直径大于4m的超大直径钢管桩。钢管桩桩径增大导致地基土体的受力与变形特征发生了变化,桩土间的相互作用机理有别于传统的小直径钢管桩,但目前对超大直径钢管桩桩土相互作用的研究尚不充分,没有成熟的土塞闭塞效应判别方法及承载力计算方法。本文针对砂土中超大直径钢管桩的桩土相互作用问题开展了理论分析、数值模拟及模型试验研究,主要研究内容概括如下:1.正确判断钢管桩在贯入过程中的土塞闭塞效应对打桩阻力及承载力的预测有重要影响。针对超大直径钢管桩的土塞闭塞效应,本文采用数值模拟方法分析了超大直径钢管桩在砂土中沉桩时桩端土体的破坏模式,确定采用梅耶霍夫公式计算桩端土体阻力,同时考虑了动力沉桩时土塞惯性力的影响,提出采用拟静力平衡法判断土塞闭塞效应,并基于打桩模型试验研究了钢管桩桩内土塞的闭塞规律。2.API规范出于安全考虑,对桩端承载力做了许多限制,因此采用API规范计算的桩基竖向承载力偏于保守。为准确判断海上风电单桩基础的竖向极限承载力,本文基于数值模拟方法揭示了超大直径钢管桩在砂土中竖向承载时桩端附近土体的受力特征,分析了桩端土拱效应对竖向承载力的影响,建立了考虑土拱效应的竖向承载力计算方法,并开展竖直向承载力模型试验验证了该方法的适用性;同时分析了不同桩径、入土桩长和壁厚钢管桩的竖直向承载力,研究了影响单桩基础竖直向承载力的特征参数。3.海洋工程中普遍采用P-Y曲线法分析桩基的水平变位,但API规范中的P-Y曲线是基于小直径桩的试桩资料得到的,对大直径桩的适用性有待研究。为得到适用于超大直径钢管桩的水平变位计算方法,本文根据数值模拟结果揭示了超大直径钢管桩在砂土中承受水平荷载时,桩身及桩周土体的受力与变形特征,针对其特有的变形形式,提出了基于圆柱壳理论的桩顶水平变位计算方法,并开展水平向承载力模型试验验证了该方法的适用性;同时分析了不同桩径、入土桩长和壁厚钢管桩的水平向承载力,研究了影响单桩基础水平向承载力的特征参数。
[Abstract]:The utilization rate of single pile foundation in offshore wind farm is more than 65%, which is the main foundation type of offshore fan. In recent years, with the increase of fan capacity and water depth, the large diameter steel pipe pile with diameter more than 4 m is widely used in offshore wind power single pile foundation. The stress and deformation characteristics of foundation soil have been changed due to the increase of steel pipe pile diameter, and the interaction mechanism between pile and soil is different from that of traditional small diameter steel pipe pile, but the research on pile-soil interaction of super-large diameter steel pipe is not enough at present. There is no mature method for judging the blocking effect and calculating the bearing capacity of soil plug. In this paper, theoretical analysis, numerical simulation and model test of pile-soil interaction of super-large diameter steel pipe piles in sand are carried out. The main research contents are summarized as follows: 1: 1. Correctly judging the plugging effect of steel pipe pile in the process of penetration has an important influence on the prediction of pile driving resistance and bearing capacity. In view of the soil plug blocking effect of super-large diameter steel pipe pile, this paper analyzes the failure mode of pile end soil when large diameter steel pipe pile is sinking in sand by using numerical simulation method, and determines to calculate the soil resistance of pile end by Meyer Hoff formula. At the same time, considering the influence of the inertia force of soil plug in dynamic piling, the quasi-static balance method is proposed to judge the blocking effect of soil plug, and based on piling model test, the blocking law of soil plug in steel pipe pile is studied. 2. The API code is considered for safety reasons. The bearing capacity of pile end is limited, so the vertical bearing capacity calculated by API code is conservative. In order to accurately judge the vertical ultimate bearing capacity of offshore wind power single pile foundation, based on the numerical simulation method, this paper reveals the stress characteristics of the soil near the pile tip when the super-large diameter steel pipe pile is loaded vertically in sand. In this paper, the influence of soil arch effect on vertical bearing capacity is analyzed, the calculation method of vertical bearing capacity considering soil arch effect is established, and the applicability of this method is verified by the model test of vertical bearing capacity, and the different pile diameter is analyzed. The vertical bearing capacity of the steel pipe pile with the length and thickness of the soil is studied, and the characteristic parameter of the vertical bearing capacity of the single pile foundation is studied. The P-Y curve method is widely used in ocean engineering to analyze the horizontal displacement of pile foundation, but the P-Y curve in API code is based on the test pile data of small diameter pile, and the applicability of P-Y curve to large diameter pile needs to be studied. In order to obtain the calculation method of horizontal displacement for super-large diameter steel pipe piles, this paper reveals the stress and deformation characteristics of the pile body and surrounding soil when the pile body and surrounding soil are subjected to horizontal load according to the numerical simulation results. Based on the theory of cylindrical shell, the calculation method of horizontal displacement of pile top is put forward, and the applicability of this method is verified by the model test of horizontal bearing capacity, and the different diameter of pile is analyzed at the same time. The horizontal bearing capacity of the steel pipe pile with the length and thickness of the soil is studied, and the characteristic parameters that affect the horizontal bearing capacity of the single pile foundation are studied.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU473.1;TU435

【参考文献】