【作者】 艾士刚；

【导师】 汤立群；

【作者基本信息】 华南理工大学 ， 固体力学， 2011， 博士

【摘要】 液体橡胶基混凝土(LRBC)是一种新型混凝土材料,其中液体橡胶基质取代了传统的水泥砂浆。液体橡胶具有很好的机械性能,与骨料之间的力学性能差异远小于普通沥青与骨料之间的差异,因此LRBC将是一种极具潜力的高性能桥面铺装材料。目前,对于LRBC材料的研究还处于探索阶段,要将之作为工程应用材料还需要进行大量的机理研究、测试和优化设计。宏观的均一方法被广泛地运用来描述混凝土类材料的性能,比如弹性模量和泊松比等等,但是,这种宏观的均一方法很难用来描述材料破坏的产生及扩展过程,因此,从细观尺度描述材料的变形和破坏特性是了解混凝土类材料破坏机理和进行材料最优化设计的关键。混凝土类材料的破坏过程是一个非常复杂而又富有挑战的课题,研究LRBC试件的变形与破坏过程对揭示混凝土类材料的力学行为及破坏机理,以及开展该新型混凝土材料性能的优化设计,具有重要的学术价值和工程价值。本文从细观结构出发,将LRBC视为由碎石骨料、液体橡胶基质及二者之间界面组成的三相复合材料,视界面层为环绕于每颗骨料表面的独立材料。通过实验测定橡胶与石料之间的粘结性能,确定界面材料的破坏参数。通过研究界面厚度值对LRBC试件力学性能的影响,确定合理的界面厚度值,建立了LRBC试件的细观结构模型。应用LS-DYNA对LRBC试件进行准静态及动态破坏分析。通过改变准静态加载速度,并将各种加载速度下得到的结果与实验结果相对比,分析了加载速度对模拟计算结果的影响,确定了合理的加载速度,为细观分析LRBC材料的破坏机理提供了途径。针对混凝土类材料宏观力学性能离散性的问题,文中从细观结构出发,通过对同等参数下一系列LRBC试件的仿真计算,研究了LRBC试件性能的离散度。指出骨料在试件内部位置分布的随机性是造成该材料试件宏观力学性能离散性的因素之一,并根据各试件的破坏方式,分析了骨料的位置分布对LRBC材料性能的影响。同时,通过改变骨料多边形边数概率统计参数,研究了骨料几何性质对LRBC材料力学性能的影响,指出了骨料多边形的几何性质对LRBC材料性能影响的规律性。在相同的配合比下,本文分别对含有不同粒径的LRBC材料试件进行了数值计算,分析了骨料粒径对LRBC材料力学性能的影响特性,证实了骨料级配的改变对混凝土类复合材料的力学性质将产生影响。此外,基于传统的级配理论,本文尝试了一系列级配设计,初步分析了级配对LRBC材料力学性能影响的规律,用数值模拟的方式代替传统的配合比实验,为该材料的优化设计打下基础。对LRBC的冲击行为,本文从细观尺度模拟仿真LRBC试件在冲击荷载作用下的变形、破坏过程。分别对惯性效应以及应变率效应对该材料试件的冲击压缩强度、冲击压缩切线模量以及试件的冲击损伤行为等特征给予了分析。更多还原

【Abstract】 The liquid rubber based concrete (LRBC) is a new kind of concrete-like composite in which the matrix is the liquid rubber substituting the conventional cement mortar. Comparing with asphalt concrete or cement concrete, LRBC has significantly different mechanical properties, which induces it to be a great potential high-performance pavement material. Currently, the investigation of the new concrete is just beginning, and plenty of testing and optimization works should be done before it present in engineering applications.The uniformization method has been widely used for depicting the material properties such as elastic modulus, Poisson’s ratio etc. Anyhow such uniformization method is hardly used to predict the failure properties. The deformation and failure features of the meso-structure under loading are keys for the investigations of the failure mechanism and the further improvement of mechanical properties of the new material. The study of the failure process of the concrete-like materials is a very complex and challenging task, the investigation of the deformation and failure fectures of the LRBC specimen has significant academic and engineering values not only for investigating the failure process and mechanism of concrete-like materials but also for the optimization of the new concrete.In the present paper, the new concrete is modelled as a three-phase composite consisting of aggregate, liquid rubber matrix and interface between the aggregate and the liquid rubber matrix. The interface is regarded as an independent material with given geometry and mechanical properties. The bonding properties between liquid rubber and stone are given by tests. The influence of the interfacial thickness on the mechanical properties were studied and compared with experimental results to give a reasonable value of the thickness of the interfacial transition zone. Commercial procedure LS-DYNA is used and the effects of the loading rates on the numerical simulation results were investigated and compared with the experimental results to identify the just one of the loading speed which ensure the simulation results accurately and increase calculation efficiency at the same time.For the discreteness of macroscopic mechanical properties of concrete-like material, six samples with same meso statistical parameters of the aggregate geometry were investigated to study the discreteness of the macro properties of the material. From the study it is found that the random distribution of aggregates is one of the reasons why different specimens have different mechanical properties while they have same aggregate ratio, same grading and even same meso-statistical parameters. Besides, the failure process and fracture features were compared among the samples with different meso-statistical parameters of aggregate geometry. The numerical results derived the influences of the aggregate geometry on the tensile and compressive strength, the meso-scopic deformation and failure features of the LRBC. By the numerical analyzes, for LRBC, clearly, it has a group of meso-statistical parameters of aggregate geometry which will lead to the best material properties.Specimens with same aggregate ratio but different aggregate sizes were tested, and the influences of the aggregate size on the mechanical properties were investigated. It confirmed the effects of the gradation on the macro-properties of the concrete-like materials. Based on the traditional grading theory, a series of aggregate gradations were designed and for each grading three specimens were constructed. Static tensile and compressive tests carried out and the influences of the aggregate grading on the mechanical properties were studied. This method should give some help for the grading optimization of the new contrete.The deformation and failure factures of the meso-structure of the new concrete under dynamic compression were simulated successfully, and the failure factures, inertial confinement effects and strain rates effects were investigated simultaneously.更多还原