砂性土打入桩桩土作用机理及竖向承载力计算方法评价
发布时间：2018-07-26 13:57
【摘要】：打入桩作为主要承重构件广泛应用于大型桥梁、海上平台、风力发电机等近海结构物,其竖向受荷特性是结构安全性能设计的重要指标之一。与陆上桩基不同,通过静载试验获得海洋桩基竖向承载力非常困难且价格昂贵,因此需要建立可靠的理论方法准确预测其竖向承载特性。基于静力触探试验(CPT)的打入桩设计方法充分地考虑了桩打入过程中桩侧应力场的变化,其可靠性已经通过大量的数据库研究工作得到了初步验证。然而模型槽试验缺少桩侧应力测量数据,现场试验无法对砂土中应力场进行测量,不能准确描述桩打入过程中桩侧应力的发展规律,桩打入过程中桩土界面特性、应力场剧烈变化及其承载力时间效应等核心问题仍有待解决,需通过精细的理论和试验分析对打入桩竖向受荷特性开展深入研究,提高打入桩设计方法的可靠性。目前打入桩桩土作用机理及竖向承载力的研究工作主要从以下三个方面入手:一、系统推进模型槽试验及现场大直径打入桩试验,采用当前最先进的试验技术,解决应力测量困难问题,揭示打入桩竖向承载力时间效应的本质机理,理清影响打入桩竖向承载力的主要因素,并用于改进主流打入桩设计方法;二、系统开展数值模拟工作,采用先进的数值模拟技术,主要包括自适应网格法(ALE),耦合的欧拉-拉格朗日法(CEL),物质点法(MPM)及离散元方法(DEM)等解决桩打入过程中的大变形问题,结合可靠的土体本构模型,准确模拟桩打入过程中的复杂应力场变化、颗粒破碎情况等特性,同时弥补现场试验的应力测量数据的不足,获得更加完整的应力场变化规律,加深对打入桩竖向受荷特性的理解;三、构建具有高代表性的打入桩静载试验数据库,对主流打入桩设计方法进行系统的数据库分析,理清最新试验研究成果的实用效果,并综合评价各主流打入桩设计方法的可靠性。本文在砂性土中打入桩桩土作用机理及竖向承载力设计方法数据库分析方面主要进行了以下研究:1、开展了对模型槽试验和大直径闭口桩的有限元模拟工作。基于Jardine教授的模型槽试验,采用Abaqus自适应网格法(ALE)开展模型桩打入过程的数值模拟工作,获得了与模型试验较为一致的结果,弥补了模型试验应力测量的不足,得到了桩打入过程中环向应力及竖向应力的变化规律,同时也验证了打入桩竖向承载力试验研究成果,如h/R效应等,理清了影响闭口打入桩竖向承载力的主要因素。此外,采用Abaqus耦合的欧拉-拉格朗日(CEL)技术对大直径闭口桩打入过程进行模拟,理清真实尺寸打入桩模拟与模型槽试验模拟的异同,验证大直径闭口桩与模型桩应力场研究结果的一致性。2、开展了真实尺寸开口桩有限元模拟工作。采用AbaqusCEL方法解决了管桩打入过程中的大变形问题,揭示了管桩打入过程中的土塞发展规律及桩侧应力场变化规律等,与经验公式和现场试验结果进行对比分析,理清了管桩竖向承载力的主要影响因素。3、组建了 ZJU-ICL砂土荷载数据库。主要通过文献搜索、国际合作及现场试桩试验搜集打入桩静载试验数据,组建了包含117根打入桩静载试验数据的数据库,是目前国际上最具代表性的砂土静载试验数据库;在此基础上,对目前国际上主流的8种打入桩设计方法进行数据库分析,对其可靠性进行系统地评价;同时对试验研究的热点问题如桩的长细比L/D、管桩D/t、时间效应等对打入桩竖向承载力的影响进行研究。4、开展了现场试桩项目研究。以芜湖长江二桥试桩项目为依托,获得了 PHC管桩静载试验数据,并及时将四种应用最广泛的CPT设计方法及美国石油协会API设计方法应用至试桩项目中,进而验证了 CPT设计方法在工程实践中的可靠性。芜湖试桩项目同时可用于打入桩竖向承载力影响因素的相关研究,填补了目前对于PHC管桩及低休止时间打入桩研究的空白。
[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.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：U443.152
，
本文编号：2146234
[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.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：U443.152
，
本文编号：2146234
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