【作者】 丁涛；

【导师】 钟红；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2013， 硕士

【摘要】 许多重大混凝土工程建立在岩石基础上。以岩基上的混凝土坝为例,坝基与混凝土的交界面是一个薄弱环节。坝踵一般是带裂缝工作的,坝踵裂缝的扩展可降低大坝抗剪强度,破坏灌浆帷幕,破坏排水系统,造成坝身泄漏,损害大坝整体性。尤其是在地震作用下,较大的拉应力可能导致已有的裂缝快速扩展,威胁大坝的安全。对混凝土大坝尤其是坝基面的断裂特性进行深入研究,对于保证高坝大库的安全具有重要意义。发生于坝踵的裂缝,可能沿坝基面扩展,也可能裂入坝体或建基面。大坝安评中多见人为假定裂缝沿界面扩展,但有研究表明,伸向地基的斜裂缝更危险。准确判定坝踵裂缝的扩展路径,方能对坝的状态做出可靠评价。采用断裂力学方法求解这一问题时,界面裂缝应力场存在多重奇异性和振荡现象,Ⅰ、Ⅱ型应力强度因子互相耦合,若仍采用断裂力学中对均质材料的裂尖应力场和位移场的计算公式是不合适的。本文借助于界面力学的相关理论,对双材料界面裂缝尖端的应力场和位移场重新进行了定义。具体以岩石与混凝土界面断裂试验的方式,对岩石与混凝土界面断裂的相关参数进行了采集,在此基础上利用大型有限元程序ANSYS并借助于界面力学的理论对岩石与混凝土界面断裂特性进行了深入的研究。论文共分为四个章节。第一章详细阐述了界面力学的基本理论,本论文的研究背景、选题的意义以及相关的研究内容。第二章介绍了试验之前的主要准备工作内容。这其中包括早期试验方案的设计,试验中需要使用的加载装置、采集系统以及各种传感器,组成试件的岩石和混凝土的相关材料参数,试验中四点剪切梁试件的制作、养护以及处理方法,试验的具体操作步骤。第三章主要介绍了试验中直接观察到的试件的断裂形态以及直接采集到的荷载与界面裂缝口位移、两个加载点处试件的挠度值。第四章利用第三章试验中采集到的界面断裂试件的最大荷载值,通过大型有限元程序ANSYS计算得到界面裂缝翼缘的位移值,然后通过界面力学理论计算得到试件发生界面断裂时的临界应力强度因子和临界应变能释放率。分别以这两个参数为基础,建立了岩石与混凝土界面断裂的两个准则：界面椭圆型破坏准则和界面断裂能G准则,为实际工程中岩石基础上混凝土结构系统断裂分析提供相关的参考。更多还原

【Abstract】 Many concrete structures are built on rock foundation. Concrete dam on rock foundation, for example, the interface between the rock foundation and concrete dam is a weak link.The dam heel generally works with cracks, and the crack propagation can reduce the shear strength of the dam, destroy the grout curtain and the drainage system. And that will result in dam leak and damage the integrity of the dam. Especially in the earthquake case, the large tensile stress may lead to the rapid propagation of existing cracks, and this will threaten the safety of the dam. Depth study of the fracture properties of the interface between the concrete dam and rock foundation is of great significance to ensure the safety of high dam and large reservoirs.Cracks in the dam heel may propagate along the dam foundation surface or split into the rock foundation. Dam safety evaluation made common to assume that the cracks propagate along the interface. But studies have shown that the cracks inclining into rock foundation are more dangerous. Only an accurate determination of the dam heel crack propagation can make a reliable assessment of the status of the dam. When using a fracture mechanics method for solving this problem, the stress field of interface crack appears multiple singularity and oscillation. The stress intensity factors for type I and type II couple with each other. And now it’s not appropriate to use the formulas for solving crack tip and displacement field of the homogeneous materials.This paper is divided into four chapters. The first chapter elaborates on basic theory of interface mechanics, the research background of the paper, the significance of the issue and related contents of the research. The second chapter describes the content of the preparation before the test. This includes early test program design, the loading device of the test as well as a variety of sensors. It also states the production, conservation and processing of four-point shear beam specimens. Finally, specific experimental steps are stated. In third chapter, cracking profiles of all specimens observed in the test are shown first, then characteristic loads of specimens and displacement of crack mouth are sorted out. In chapter four, based on the maximum loads shown in last chapter, displacement of the interface crack flanges can be calculated by the finite element program ANSYS. Then critical stress intensity factors and critical stain energy release rates are obtained based on the theory of interface mechanics. Finally, two criteria are proposed based on these two parameters. They are the interface elliptic failure criterion and interfacial fracture energy criterion, and they can provide relevant reference for fracture analysis of concrete structures on rock foundation.更多还原