液化侧向扩展场地桩—土体系地震模拟反应分析

发布时间：2018-03-24 05:11

本文选题：桩基　切入点：桩-土相互作用　出处：《哈尔滨工业大学》2016年博士论文

【摘要】：地震中液化引发场地侧向扩展是导致桩基震害的主要原因之一。振动台试验是研究液化侧向扩展场地桩-土动力相互作用最有效的途径之一。数值计算是振动台试验的有力补充,同时也是将理论研究工作拓展到实际工程的必要技术环节。然而,目前研究工作更多集中于室内试验的数值计算和拟静力计算,应用于实际工程尚缺乏充分的试验与理论依据。鉴于此,本文针对地震下液化侧向扩展场地桩-土相互作用体系,通过大型桩基振动台试验和理论分析相结合的方法,建立液化侧向扩展场地桩-土动力相互作用简化分析方法并提出桩-土界面连接方式。同时,将该连接应用于液化侧向扩展场地桩基振动台试验数值分析,研究数值模型的主要影响因素。此外,考虑桩基非线性和侧向扩展大变形会导致计算量增大,为提高计算效率,建立群桩振动台试验并行数值模型,并验证其可靠性。最后,将该方法应用于实际液化侧向扩展场地预应力混凝土群桩的数值模拟。具体研究内容、方法及成果如下:1.大型液化侧向扩展场地桩基(单桩和群桩)振动台试验。针对典型近岸液化侧向扩展场地特点,借鉴同类振动台试验设计经验,通过设置岸壁触发砂土液化侧向扩展,成功实现了动力输入下砂土液化侧向扩展,并对液化侧向扩展场地土层孔压、加速度和侧向扩展位移及桩的侧向位移和弯矩响应进行系统分析。2.液化侧向扩展场地单桩简化分析方法。针对单桩基振动台试验,基于非线性Winkler地基梁模型,采用弹性梁单元模拟桩,修正的p-y弹簧单元模拟液化土体,零长度单元模拟桩底连接,将试验记录的侧向扩展位移作为p-y弹簧单元外侧节点的位移剖面,建立了液化侧向扩展场地桩-土相互作用简化分析方法,基于试验结果对简化分析方法的可靠性进行验证;并分析了桩模量、桩径和桩底刚度对桩基响应的影响。3.桩-土界面连接方式。在刚性桩-土界面连接的基础上,通过定义界面的剪切屈服力和增加并联的两类零长度单元,模拟地震过程中桩-土界面剪切力的耦合效应,实现桩-土界面的滑移,避免土体液化侧向扩展过程中桩上产生过大的轴向力。4.液化侧向扩展场地单桩基振动台试验数值模拟。针对单桩基振动台试验,利用初始状态分析法,通过施加节点孔压和相应节点荷载模拟自由水体,采用并列线性梁单元模拟岸壁,基于上述的桩-土界面连接方法,建立了液化侧向扩展场地单桩基振动台数值模型,并基于振动台试验结果对数值模型的可靠性进行验证;在此基础上,分析了阻尼系数、渗透系数和上部结构配重对桩-土动力相互作用的影响。5.液化侧向扩展场地群桩基振动台试验数值模拟。在单桩基振动台数值模型的基础上,将单桩体系转变为群桩体系,建立相应的群桩振动台数值模型,并验证其有效性。基于此,考虑混凝土桩基的非线性,建立了群桩基振动台试验的并行计算数值模型,并基于串行数值计算结果验证并行计算方法的可靠性,重点分析了群桩的弯矩-曲率和纤维应变响应特性。6.实际液化侧向扩展场地预应力混凝土群桩基数值模拟。考虑混凝土桩预应力的特点,数值模拟中,将预应力混凝土桩和土体单独建模,确保预应力作用下混凝土桩自由变形,同时在重力作用下土体位移置零。在此基础上,采用上述桩-土界面连接单元组装桩和土体模型,建立实际液化扩侧流场地预应力混凝土群桩基并行计算数值模型,并分析地震下桩基的轴力、剪力、弯矩、曲率和纤维应变响应特性。本文研究成果进一步加深对液化侧向扩展场地桩基地震响应特性和震害问题的理解。尤其是所完成的液化侧向扩展场地桩基大型振动台试验、针对试验所做的大量的数值模拟分析和实际液化侧向扩展场地群桩基并行计算数值模拟分析,以及分析所获得的一些认识。这将为同类试验和数值模拟研究提供必要技术细节,对于进一步深入研究液化侧向扩展场地桩基地震响应特性具有重要意义,并为逐步完善液化侧向扩展场地桩基抗震设计积累宝贵的基础资料。
[Abstract]:The earthquake caused liquefaction ground lateral expansion is one of the main causes of pile damage. Shaking table test study on liquefaction lateral spreading ground soil pile dynamic interaction is one of the most effective way. Numerical calculation is a strong complement of shaking table test, but also the theoretical research work to expand the essential technology to practical engineering. However, numerical research now is more focused on laboratory tests and pseudo static, applied to practical engineering test and lack of sufficient theoretical basis. In view of this, based on the lateral seismic liquefaction to expand the field of pile-soil interaction system, combining the large shaking table experiments and theoretical analysis of pile foundation, establish liquefaction the lateral extension of site soil pile dynamic interaction analysis method is proposed to simplify the pile-soil interface connection. At the same time, the connection is applied to lateral expansion liquefaction Analysis of pile vibration table test to show the numerical research the main influencing factors of numerical model. In addition, expansion of large deformation will lead to increase the amount of calculation of pile foundation considering the nonlinearity and the lateral, in order to improve the calculation efficiency, the establishment of group pile shaking table test of parallel numerical model, and verify its reliability. Finally, the method is applied to the actual liquefaction the lateral extension of numerical simulation of concrete pile site prestressed concrete research content, methods and results are as follows: 1. large liquefaction lateral spreading site pile (single pile and pile group). The shaking table test for typical offshore liquefaction lateral expansion characteristics of the site, from the same vibration test design experience, by setting the wall of sand liquefaction lateral spreading the successful implementation of the power input, lateral sand liquefaction and lateral spreading of liquefaction expansion, soil pore water pressure, lateral displacement and lateral displacement and acceleration expansion pile And the moment response system analysis of.2. liquefaction lateral spreading ground pile. The simplified analysis method for single pile vibration table test, nonlinear Winkler model based on the elastic foundation beam, beam element to simulate pile, p-y spring element simulation of the liquefied soil amendment, zero length element simulation of pile bottom connection, the lateral displacement as expansion of the test record the displacement profile p-y lateral spring element node, establish the liquefaction lateral spreading field of pile-soil interaction simplified analysis method based on the test results, verify the reliability of the simplified analysis method; and the analysis of the pile modulus, pile diameter and pile stiffness of pile foundation response.3. pile-soil interface based on connection. Rigid pile soil interface connection, two types of zero length element through the shear interface definition of yield force and increase the parallel coupling, pile-soil interface shear stress in the process of earthquake simulation The slip effect, pile-soil interface, avoid soil liquefaction lateral spreading process of pile on excessive axial force.4. liquefaction lateral spreading numerical simulation of single pile ground shaking table test for single pile vibration table test, using the method of initial state, by applying nodal pore pressure and the corresponding node load simulation of free water. Using the parallel linear beam element to simulate the wall connection method of pile-soil interface based on established liquefaction lateral spreading numerical field single pile vibration table model, and based on the results of shaking table test to verify the reliability of the numerical model; on this basis, analysis of the damping coefficient, permeability coefficient and mass of superstructure on the pile soil dynamic interaction.5. liquefaction lateral spreading simulation site pile foundation vibration test. Numerical basis of numerical model in single pile vibration table, the single pile system into Pile group system, the establishment of numerical pile shaking table model accordingly, and verifies its validity. Based on this, considering the nonlinear concrete pile foundation, pile foundation established parallel vibration test and numerical calculation model, calculation results verify the reliability of parallel computing method based on serial numerical analyses of Moment Curvature of pile group and the fiber strain response of the.6. actual liquefaction lateral spreading numerical simulation of prestressed concrete pile foundation site. Considering the characteristics of prestressed concrete pile, numerical simulation, the prestressed concrete pile and soil are modeled separately, ensure the prestressed concrete pile under free deformation, while in soil under the action of gravity position zero displacement. On this basis, using the above pile soil interface connecting unit assembled pile and soil model, establish the actual liquefaction expansion numerical model of flow field of parallel side prestressed concrete pile foundation, and Analysis of the axial force of the pile foundation under seismic shear force, bending moment, curvature and fiber strain response characteristics. The results of this study further expansion characteristics and understand the problem of earthquake response of pile foundation on seismic liquefaction lateral site. Especially the liquefaction induced lateral vibration of large pile extension site test, a large number of tests made for numerical simulation analysis and actual liquefaction lateral spreading parallel computing numerical simulation analysis of soil pile foundation, and some understanding of the analysis. This will provide the necessary technical details for the test and numerical simulation study of similar, for further study on liquefaction lateral spreading plays an important role in the response characteristics of pile foundation seismic site, and gradually improve the liquefaction lateral spreading ground pile seismic design of accumulated precious data.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TU473.1;TU435

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