本文選題：超大直徑 + 鋼管樁　； 參考：《天津大學(xué)》2014年碩士論文

【摘要】：單樁基礎(chǔ)在海上風(fēng)電場中的使用率占65%以上,是海上風(fēng)機(jī)的主要基礎(chǔ)型式。近年來,隨著風(fēng)機(jī)單機(jī)容量增大及建設(shè)水深增加,海上風(fēng)電單樁基礎(chǔ)普遍采用直徑大于4m的超大直徑鋼管樁。鋼管樁樁徑增大導(dǎo)致地基土體的受力與變形特征發(fā)生了變化,樁土間的相互作用機(jī)理有別于傳統(tǒng)的小直徑鋼管樁,但目前對超大直徑鋼管樁樁土相互作用的研究尚不充分,沒有成熟的土塞閉塞效應(yīng)判別方法及承載力計算方法。本文針對砂土中超大直徑鋼管樁的樁土相互作用問題開展了理論分析、數(shù)值模擬及模型試驗研究,主要研究內(nèi)容概括如下:1.正確判斷鋼管樁在貫入過程中的土塞閉塞效應(yīng)對打樁阻力及承載力的預(yù)測有重要影響。針對超大直徑鋼管樁的土塞閉塞效應(yīng),本文采用數(shù)值模擬方法分析了超大直徑鋼管樁在砂土中沉樁時樁端土體的破壞模式,確定采用梅耶霍夫公式計算樁端土體阻力,同時考慮了動力沉樁時土塞慣性力的影響,提出采用擬靜力平衡法判斷土塞閉塞效應(yīng),并基于打樁模型試驗研究了鋼管樁樁內(nèi)土塞的閉塞規(guī)律。2.API規(guī)范出于安全考慮,對樁端承載力做了許多限制,因此采用API規(guī)范計算的樁基豎向承載力偏于保守。為準(zhǔn)確判斷海上風(fēng)電單樁基礎(chǔ)的豎向極限承載力,本文基于數(shù)值模擬方法揭示了超大直徑鋼管樁在砂土中豎向承載時樁端附近土體的受力特征,分析了樁端土拱效應(yīng)對豎向承載力的影響,建立了考慮土拱效應(yīng)的豎向承載力計算方法,并開展豎直向承載力模型試驗驗證了該方法的適用性;同時分析了不同樁徑、入土樁長和壁厚鋼管樁的豎直向承載力,研究了影響單樁基礎(chǔ)豎直向承載力的特征參數(shù)。3.海洋工程中普遍采用P-Y曲線法分析樁基的水平變位,但API規(guī)范中的P-Y曲線是基于小直徑樁的試樁資料得到的,對大直徑樁的適用性有待研究。為得到適用于超大直徑鋼管樁的水平變位計算方法,本文根據(jù)數(shù)值模擬結(jié)果揭示了超大直徑鋼管樁在砂土中承受水平荷載時,樁身及樁周土體的受力與變形特征,針對其特有的變形形式,提出了基于圓柱殼理論的樁頂水平變位計算方法,并開展水平向承載力模型試驗驗證了該方法的適用性;同時分析了不同樁徑、入土樁長和壁厚鋼管樁的水平向承載力,研究了影響單樁基礎(chǔ)水平向承載力的特征參數(shù)。
[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.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU473.1;TU435

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