【作者】 王刚；

【导师】 马震岳；

【作者基本信息】 大连理工大学 ， 水利水电工程， 2008， 博士

【摘要】 早期建造的混凝土重力坝随着龄期的增长,坝体的老化特征日益严重和突出,寻求解决坝体老化问题的理论研究与工程处理措施变得越来越重要和紧迫。大坝老化隐患的研究需要对多种老化现象及其根源进行详细分析,相关的理论研究可以形成一个系统的理论体系。本论文就与长服役期混凝土重力坝纵缝力学特性相关的大坝整体安全性问题及坝体修复加固措施的数值仿真分析方法进行了详细研究,具体包括如下几项研究内容:基于长服役期混凝土重力坝纵缝中存在大量堆积、沉淀物质的特殊现象(因早期施工原因和坝体老化而出现的一种特殊的工程现象),提出了该类型接缝的有限元数值计算模型。根据有限元接触力学基本理论建立了适合模拟这种纵缝结构的具有厚度的接触面单元(接缝单元),该单元不仅能够模拟纵缝接触界面的张开、闭合与滑移特性,还能考虑缝内物质的本构关系,尤其是在接缝单元的法向刚度特性上提供了新的计算模式,既能有效地控制法向嵌入,又能较好地模拟出接缝单元的法向受力特性:在有限元求解方法上,通过采用增量迭代法实现了强度校核时的结点不平衡力计算与控制单元法向嵌入时的接触状态调整同步进行。在这些研究的基础上编制了简单实用的有限元求解程序Joint 2D,通过数值算例验证了该程序的接触界面模拟能力和计算精度。之后,将该程序应用到实际工程问题中,明确了纵缝界面不同力学参数对纵缝结合程度的影响。在实际工程中,混凝土重力坝接缝特征力学参数的确定是工程接触力学应用的难点。已有的研究表明,基于计算智能的位移反分析方法是一种非常有效的参数反演方法,采用智能化反演分析方法确定大坝接缝的力学参数是一个新兴的课题。本论文在对重力坝纵缝这一非线性结构的力学特性参数进行分析研究后,提出了基于遗传算法的优化反演方法,创新性地实现了带纵缝重力坝坝体弹性参数及坝体纵缝摩擦系数两个方面参数的联合反演。在研究过程中,应用了两个强有力的工具:一个是用于模拟纵缝的大型通用有限元软件ANSYS中的面一面接触单元,ANSYS中采用高效的接触迭代算法可合理、有效地求解纵缝接触问题,这为纵缝的合理模拟和接触界面参数的识别提供了强有力的保障:另一个是遗传算法,它是目前计算智能方法中相对最为成熟的一种算法。本论文通过数据接口实现了两个工具的有机结合。相应的研究结果证明了本论文提出的联合反演方法的高效性、合理性与实用性,可为明确纵缝的力学特性及其对坝体整体安全性的影响提供了一种有效手段。本论文还提出了接触非线性坝体结构的静、动荷载组合作用的实用分析方法体系,用于带纵缝混凝土重力坝抗震特性分析。该方法体系主要包括LS-DYNA3D程序的显式动力学有限元方法,模拟纵缝的对称罚函数接触算法,考虑结构—地基相互作用的黏弹性人工边界以及该边界上地震波动的输入方法,结构静力问题的动力学求解方法四项主要内容。本论文对该方法体系中的关键问题进行了理论推导和算例证明。相关研究表明,该方法体系计算效率高,计算过程容易实现,可为求解大型工程问题提供有效的解决方案。然后,采用该方法体系对带纵缝混凝土重力坝的静、动力特性进行了分析,研究了纵缝在静、动力荷载作用下的反应特性及其对大坝抗震性能的影响。最后,本论文提出了既能模拟大体积混凝土动态施工方式、施工进度计划,又能够模拟边界条件、荷载、材料性能的变化,尤其是能够对施工过程中坝体结构温度变化和新浇混凝土的热力学影响进行计算分析的大坝修复加固施工数值仿真分析方法。该方法的技术手段是以大型商业通用有限元软件ANSYS为计算平台,利用该软件自带的APDL(ANSYS Program Design Language)程序语言进行二次开发,编写施工过程有限元数值仿真程序。本论文结合长服役期混凝土重力坝的创新性全面修复加固方案——坝体内置换混凝土防渗墙加固方案,编写了针对该方案的施工过程数值仿真程序,并利用该仿真程序研究了方案施工期的坝体结构安全性状况,明确了方案施工过程中的部分关键施工技术问题和所需采用的安全措施,为修复加固方案的论证和实施提供了理论支撑。更多还原

【Abstract】 More and more serious aging problems have appeared in early constructed concrete dams with their age increasing, so the theoretical research and engineering treatments for solving aging problems of the dam have become more and more important and emergent. Aging phenomena and their origins must be studied in detail and the relative theoretical work can form a theory system. In this dissertation, the main subject is about the mechanical behavior analysis of a long-term operating concrete gravity dam with longitudinal joints and numerical simulation of its reinforcing and regenerating construction using Finite Element Method （FEM）. The major contributions are summarized as follows:A typical characteristic of the longitudinal joints of the long-term operating dam is that many deposits and sediments are in the joints caused by early worse construction and aging of the dam concrete. Based on analyzing of the normal and shear characteristics of the longitudinal joints of the dam, the constitutive model of this type of longitudinal joint is provided, especially a new normal constitutive function is developed reasonably for contact surface elements with thickness simulating such joints, and then all of the ideas are written in a nonlinear finite element code, Joint₂D, including increment iterating method. The non-balance force at each node and the normal penetration of the two interfaces of each joint element are adjusted simultaneously in the code, and three testified examples prove it is reliable, precise and general. Furthermore, the actual gravity dam with longitudinal joints is numerical simulated, and the variation of the resultant deformation and stress distributions of the dam are analyzed definitely by changing different key mechanical parameters of the joint elements, and some valuable conclusions are obtained reasonably.In fact, analysis of the longitudinal joint in numerical simulation is a kind of nonlinear contact problem and the joints are always modeled by contact elements in FEM. However, it is a difficult problem to determine directly the mechanical parameters about these contact elements. Herein, a new displacement inverse method based on calculating intelligent method is provided to identifying the elastic parameters of the dam body and the frictional coefficients of the joints. During the inverse calculating process, the surface-to-surface contact element, which is developed in ANSYS solving by efficient iterating contact algorithm, has been used to simulate the longitudinal joint of the dam. Also, genetic algorithm （GA） is utilized in the inverse process since GA is a much more mature and more reliable one among many calculating intelligent methods. In the displacement inverse method, the surface-to-surface element and GA are two powerful tools assuring the whole inverse process is performed successfully and efficiently. The calculating results indicate that the inverse procedure is reasonable, efficient, and reliable, and can be successfully applied to obtain the frictional coefficients of the longitudinal joints of the actual gravity dam or other similar dams.A methodological system, which includes explicit time integration dynamic finite element method （developed in LS-DVNA3D codes）, symmetric penalty method, visco-spring dynamic artificial boundary method, and method of static load response being calculated by dynamic codes, is introduced in detail and applied to solve the nonlinear static and dynamic responses of the structural system composed from the aging concrete gravity dam and the rock foundation, as a result that the combined action of dynamic and static loads is performed and the characteristic responses of these joints are obtained reasonably and easily. It proves that the methodological system can be used to settle the complex and large-scale engineering project feasibly and efficiently.Finally, a numerical simulation method of structural construction is provided about modeling constructing technique, constructing schedule, and as well as the variation of the boundary situation, loads and material behavior during process of construction for mass concrete structures. Based on the new reinforcing and regenerating technique for the long-term operating concrete dam and the numerical simulation method mentioned above, constructing process modeling and safety analyzing are performed utilizing the FE software, ANSYS, which has its own program design language, APDL, to make a constrction simulating program. The conclusion are drawn resonablly and the simulating method could provide suggestion about constructing treatments not only to this engineering but also to other similar projects since it can predict the systematic safety of dam construction and provide effective reference for technique of construction.更多还原