【摘要】：打入樁作為主要承重構件廣泛應用于大型橋梁、海上平臺、風力發(fā)電機等近海結構物,其豎向受荷特性是結構安全性能設計的重要指標之一。與陸上樁基不同,通過靜載試驗獲得海洋樁基豎向承載力非常困難且價格昂貴,因此需要建立可靠的理論方法準確預測其豎向承載特性�；陟o力觸探試驗(CPT)的打入樁設計方法充分地考慮了樁打入過程中樁側應力場的變化,其可靠性已經通過大量的數據庫研究工作得到了初步驗證。然而模型槽試驗缺少樁側應力測量數據,現(xiàn)場試驗無法對砂土中應力場進行測量,不能準確描述樁打入過程中樁側應力的發(fā)展規(guī)律,樁打入過程中樁土界面特性、應力場劇烈變化及其承載力時間效應等核心問題仍有待解決,需通過精細的理論和試驗分析對打入樁豎向受荷特性開展深入研究,提高打入樁設計方法的可靠性。目前打入樁樁土作用機理及豎向承載力的研究工作主要從以下三個方面入手:一、系統(tǒng)推進模型槽試驗及現(xiàn)場大直徑打入樁試驗,采用當前最先進的試驗技術,解決應力測量困難問題,揭示打入樁豎向承載力時間效應的本質機理,理清影響打入樁豎向承載力的主要因素,并用于改進主流打入樁設計方法;二、系統(tǒng)開展數值模擬工作,采用先進的數值模擬技術,主要包括自適應網格法(ALE),耦合的歐拉-拉格朗日法(CEL),物質點法(MPM)及離散元方法(DEM)等解決樁打入過程中的大變形問題,結合可靠的土體本構模型,準確模擬樁打入過程中的復雜應力場變化、顆粒破碎情況等特性,同時彌補現(xiàn)場試驗的應力測量數據的不足,獲得更加完整的應力場變化規(guī)律,加深對打入樁豎向受荷特性的理解;三、構建具有高代表性的打入樁靜載試驗數據庫,對主流打入樁設計方法進行系統(tǒng)的數據庫分析,理清最新試驗研究成果的實用效果,并綜合評價各主流打入樁設計方法的可靠性。本文在砂性土中打入樁樁土作用機理及豎向承載力設計方法數據庫分析方面主要進行了以下研究:1、開展了對模型槽試驗和大直徑閉口樁的有限元模擬工作�；贘ardine教授的模型槽試驗,采用Abaqus自適應網格法(ALE)開展模型樁打入過程的數值模擬工作,獲得了與模型試驗較為一致的結果,彌補了模型試驗應力測量的不足,得到了樁打入過程中環(huán)向應力及豎向應力的變化規(guī)律,同時也驗證了打入樁豎向承載力試驗研究成果,如h/R效應等,理清了影響閉口打入樁豎向承載力的主要因素。此外,采用Abaqus耦合的歐拉-拉格朗日(CEL)技術對大直徑閉口樁打入過程進行模擬,理清真實尺寸打入樁模擬與模型槽試驗模擬的異同,驗證大直徑閉口樁與模型樁應力場研究結果的一致性。2、開展了真實尺寸開口樁有限元模擬工作。采用AbaqusCEL方法解決了管樁打入過程中的大變形問題,揭示了管樁打入過程中的土塞發(fā)展規(guī)律及樁側應力場變化規(guī)律等,與經驗公式和現(xiàn)場試驗結果進行對比分析,理清了管樁豎向承載力的主要影響因素。3、組建了 ZJU-ICL砂土荷載數據庫。主要通過文獻搜索、國際合作及現(xiàn)場試樁試驗搜集打入樁靜載試驗數據,組建了包含117根打入樁靜載試驗數據的數據庫,是目前國際上最具代表性的砂土靜載試驗數據庫;在此基礎上,對目前國際上主流的8種打入樁設計方法進行數據庫分析,對其可靠性進行系統(tǒng)地評價;同時對試驗研究的熱點問題如樁的長細比L/D、管樁D/t、時間效應等對打入樁豎向承載力的影響進行研究。4、開展了現(xiàn)場試樁項目研究。以蕪湖長江二橋試樁項目為依托,獲得了 PHC管樁靜載試驗數據,并及時將四種應用最廣泛的CPT設計方法及美國石油協(xié)會API設計方法應用至試樁項目中,進而驗證了 CPT設計方法在工程實踐中的可靠性。蕪湖試樁項目同時可用于打入樁豎向承載力影響因素的相關研究,填補了目前對于PHC管樁及低休止時間打入樁研究的空白。
[Abstract]:As the main load-bearing components, it is widely used in large bridges, offshore platforms, wind turbines and other offshore structures. The vertical loading characteristics are one of the most important indicators for the design of structural safety. A reliable theoretical method is used to accurately predict the vertical bearing capacity of the pile. Based on the static penetration test (CPT), the pile driving design method fully considers the change of the pile side stress field in the pile driving process. Its reliability has been preliminarily verified by a large number of database research work. However, the model trough test lacks the data of the pile side stress measurement. The field test can not be used to measure the stress field in the sand, and it can not accurately describe the development law of the pile side stress in the process of pile entry. The core problems of the pile and soil interface characteristics, the violent change of the stress field and the time effect of the bearing capacity of the pile still need to be solved. In order to improve the reliability of the design method of pile driving, the research work on the action mechanism and the vertical bearing capacity of pile pile soil is mainly from the following three aspects: first, the system propulsion model groove test and the field large diameter entry pile test are carried out, and the problems of stress measurement are solved by the first test technology, and the problem of stress measurement is solved. The essential mechanism of the time effect of the vertical bearing capacity of the pile is shown to clarify the main factors affecting the vertical bearing capacity of the pile, and to improve the design method of the mainstream entry pile. Two, the system carries out the numerical simulation work and uses the advanced numerical simulation technology, mainly including the adaptive grid method (ALE), the coupled Euler Lagrange method (CEL), the material. The point method (MPM) and the discrete element method (DEM) are used to solve the large deformation problem in the process of pile entry. Combined with the reliable soil constitutive model, the complex stress field changes and particle breakage in the pile driving process are accurately simulated, and the shortage of the stress measurement data in the field test is made up, and a more complete stress field change law is obtained. A deep understanding of the vertical loading characteristics of the pile driving pile; three, to construct a highly representative database for static loading test of pile into the pile, to carry out a systematic database analysis on the design method of the mainstream entry pile, to clarify the practical effect of the latest experimental research results and to evaluate the reliability of the design methods of the main main entry piling. The following research is made in the database analysis of the mechanism of pile and soil and the design method of vertical bearing capacity. 1, the finite element simulation of the model groove test and the large diameter closed pile is carried out. Based on the model groove test of Professor Jardine, the Abaqus adaptive grid method (ALE) is used to carry out the numerical simulation of the model pile driving process. The result is consistent with the model test, which makes up the insufficiency of the stress measurement of the model test, and obtains the change law of the cyclic stress and the vertical stress in the pile driving process. At the same time, the test results of the vertical bearing capacity of the entry pile, such as the h/R effect, have been proved to clarify the main factors that affect the vertical bearing capacity of the closed entry pile. In addition, the Abaqus coupled Euler Lagrange (CEL) technology is used to simulate the entry process of large diameter closed pile, to clarify the similarities and differences between the real size of the pile simulation and the model trough test simulation, to verify the consistency of the results of the study on the stress field of the large diameter closed pile and the model pile, and to carry out the finite element simulation of the real size open pile. The large deformation of pipe pile was solved by AbaqusCEL method, the law of soil plug development and the variation law of stress field in the pile side were revealed. The main influencing factors of the vertical bearing capacity of the pipe pile,.3, were clarified, and the ZJU-ICL sand soil load database was established. Through literature search, international cooperation and field test pile test, the data of static load test of pile into pile is collected, and the database containing 117 static load test data is set up. It is the most representative database of static load test in the world at present. On this basis, the data of 8 kinds of pile driving design methods in the world are carried out on this basis. The reliability of the test research is systematically evaluated. At the same time, the hot issues of the test research, such as the length of pile ratio L/D, the pipe pile D/t, the time effect on the vertical bearing capacity of the entry pile, are studied.4, and the research on the site test pile is carried out. The static load test data of the PHC pipe pile are obtained on the basis of the test pile items of the Second Yangtze River Bridge in Wuhu. In time, the four most widely used CPT design methods and the API design method of the American Petroleum Association are applied to the test pile project, and the reliability of the CPT design method in the engineering practice is verified. The Wuhu test pile project can be used to study the influence factors of the vertical bearing capacity of the entry pile at the same time, filling the current PHC pipe pile and the low end. The study of time into the pile is blank.
【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：U443.152
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本文編號：2146234