Constitutive Modeling of the Dynamic Anisotropic Response of Soils

本研究项目将研究土体在地震荷载作用下的应力-应变(本构)行为，重点是各向异性响应。虽然已经提出了一些模型，但对这些模型的验证是困难的。这个项目涉及一个分析、计算和实验相结合的程序来确定本构行为。分析部分侧重于首席调查员一直在开发的分层模型。该项目的实验阶段将使用多轴立方体装置，该装置能够沿着不同的加载路径加载试件。将使用超声波方法来测量土样的各向异性程度。立方体装置将被修改，以便在加载、卸载和重新加载期间可以测量各向异性的程度。还将考虑超声波方法的另一种替代方法，即测量样品的电性能。上述测试将首先进行静态测试，验证后将扩展到动态加载的情况。这将在一些土壤上进行，以验证这项技术适用于各种地质材料。最后，将本构关系用于求解典型的土体非线性边值问题。例如，将考虑动载结构-基础系统的问题，或者在无粘性土中嵌入基桩的问题。然后，将计算的结构-土壤系统的响应与现有的闭合形式解和实验室或现场数据进行定性比较。首席研究员在制定地质材料本构行为方面具有国际声誉。他拥有成功完成拟议研究的专门知识和机构设施。

This research project will investigate the stress-strain (constitutive) behavior of soils when subjected to earthquake loading, focusing on the anisotropic response. Although a number of models have already been proposed, verification of such models is difficult. This project involves a combined analytical, computational, and experimental program to determine the constitutive behavior. The analytical component focuses on a hierarchical model that the principal investigator has been developing. The experimental phase of the project will utilize a multiaxial cubical device which is capable of loading the specimen along various loading paths. An ultrasonic method will be used to measure the degree of anisotropy of the soil specimen. The cubical device will be modified so that the degree of anisotropy can be measured during loading, unloading, and reloading. An alternative to the ultrasonic method will also be considered, namely measurement of the electrical properties of the specimen. The above tests will first be done statically, and when verified they will then be extended to the case of dynamic loading. This will be done with a number of soils so as to verify the technique for a wide variety of geological materials. Finally, the constitutive characterization will be utilized to solve typical boundary value problems involving nonlinear soil behavior. For example, the problem of dynamically loaded structure-foundation systems, or of a foundation pile embedded in cohesionless soil will be considered. Then the computed response of the structure-soil system will be compared qualitatively with available closed-form solutions and laboratory or field data. The principal investigator has an international reputation in the formulation of the constitutive behavior of geological materials. He has the expertise and the institutional facilities available to successfully complete the research proposed.