【作者】 侯文峻；

【导师】 张建民；

【作者基本信息】 清华大学 ， 土木工程， 2008， 博士

【摘要】 土与结构接触面三维力学特性研究是对土与结构系统进行合理的三维化非线性分析中迫切需要解决的重点和难点问题之一。本文从研制设备入手,在材料试验、机理分析、模型建立、数值实现和工程应用等多个方面,着重对三维加载条件下接触面的静动力变形规律及其本构描述展开了较为系统而深入的探索,取得了如下的主要新成果:(1)成功研制了一台可进行三维加载的大型接触面力学特性试验机,并对其功能进行了扩展。该试验机加载能力高,可进行较大尺寸试样的接触面三维直剪和单剪试验,特别适于粗粒土与结构接触面的研究。试验机加载和测量精度高,可进行细观测量,同时还具有土的大型直剪、单剪和压缩试验功能。(2)系统地进行了多种加载条件下粗粒土与结构接触面三维静动力特性试验,得到了系列化的试验成果。将接触面的三维加载条件划分为直线型、旋转型和组合型三种不同加载类型,分别进行了单调和往返两类剪切试验,研究了法向边界条件、加载幅值、控制方式等因素对接触面力学特性的定量影响。(3)揭示了三维加载条件下粗粒土与结构接触面的基本静动力学规律及主要影响因素。研究发现,三维加载条件下接触面的强度受加载路径影响较小;循环加载引起接触面明显的硬化且在初始加载阶段发展较快;三维加载条件下接触面变形存在明显的非共轴现象;三维加载剪切引起的接触面法向位移可以划分成可逆性和不可逆性两部分;三维加载条件下接触面存在明显的物态演化,其对于接触面的力学特性有重要影响。(4)提出了合理的建模思路,在变形规律分析基础上建立了一个新的接触面三维弹塑性循环本构模型。将三维加载产生的塑性变形分为线性加载分量和旋转加载分量两部分,并对旋转加载分量提出了一种有效的描述方法。模型可有效模拟多种复杂加载路径下接触面从小变形到大变形的主要三维力学特性。(5)实现了基于新建立的接触面三维本构模型的数值计算方法并应用于边值问题分析。对面板堆石坝这一存在三维接触面问题的典型工程课题进行了三维有限元分析,验证了接触面三维本构模型数值实现的有效性和合理性。更多还原

【Abstract】 Based on the new experimental observations under three-dimensional loading conditions, a rational approach was explored systematically on the three-dimensional monotonic and cyclic behaviors of soil-structure interfaces from aspects of physical interpretations, constitutive model, and numerical implementation as well as practical application. The main achievements obtained in the thesis are as follows:1. A new, large-scale multifunction test apparatus was designed and developed to investigate the three-dimensional monotonic and cyclic behaviors of soil-structure interfaces. The maximum normal loading capacity is 800kN; and the maximum diameter of the circular sample is 500mm. Either direct shear or simple shear interface tests can be conducted using different soil containers. Various loading paths can be applied with an accurate three-dimensional loading device supported by a hydraulic servo system. Many tests on coarse-grained soil can also be conducted with the apparatus, including direct shear, simple shear and confined compression tests.2. Series of tests were systematically conducted on the interfaces between a steel plate and gravel under three-dimensional loading conditions. The monotonic and cyclic tests were performed under three kinds of loading paths, i.e., linear loading path, rotational loading path, and their combination. The tests, subjected to an application of displacements or loads, controlled in two perpendicular tangential directions, were conducted under different normal boundary conditions, including constant stress, constant displacement and constant stiffness. The effects of loading conditions were investigated carefully, including magnitude of loading, normal stress and normal stiffness.3. The fundamental rules of three-dimensional monotonic and cyclic behaviors of the interface have been studied on the basis of test results. The shear strength is insignificantly affected by the different loading paths. During the loading process, the physical states changed and governed the stress-strain response strongly. Strain-hardening occurs due to cyclic loading. Non-coaxial angle exists when the interface was subjected to a rotational loading. The volumetric strain due to dilatancy is composed of a reversible dilatancy component and an irreversible dilatancy one.4. A new three-dimensional cyclic constitutive model of the soil-structure interface was developed using the bounding surface and generalized plasticity theory based on the fundamental rules. The loading mechanism is rationally decomposed into linear and rotational loading, and a new method for evaluating the interface behavior related with the rotational loading was proposed. The present model is confirmed to capture the main features of the interface subjected to three-dimensional loading, from small strain to large strain.5. The finite element formulations of the present model was developed and implemented in a three-dimensional nonlinear FEM code. A concrete-faced rockfill dam was analyzed using the present constitutive model of the interface. The results confirmed the effectiveness of the model and the numerical implementation in the analysis of boundary-value problems involving soil-structure interfaces.更多还原