Towards an Integrated Computational-Experimental Laboratory Testing Framework for Soil Behavior Characterization and Modeling

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。地面上或地面内的任何基础设施的建设将使周围的土壤承受复杂的荷载模式。为了了解建筑物或隧道等基础设施要素的短期和长期行为，因此必须表征周围土壤的响应。对于岩土工程边值问题的求解，必须建立一个能准确反映土在一般荷载模式下的力学行为的土材料模型。现有的实验室测试被假定为代表一个单一的元素和应力应变路径，并不涵盖在边界值问题中经历的加载路径的全部范围，并且通常不足以验证材料模型在一般加载条件下的性能。在这个框架内，实验室测试将被视为一个边值问题，而不是一个单一的元素测试。该测试是再加上一个进化的逆分析方法，将允许提取大量的应力-应变路径内产生的边界值问题。一个土壤特定的材料本构模型可以从这些信息中产生。该试验装置是对目前广泛使用的三轴试验箱的改进。该装置包括横向约束，除了摩擦帽，以诱导非均匀的应力-应变状态的土壤试样。该设备将与成像技术相结合，以捕获加载过程中样本的三维变形形状。新的反分析算法，SelfSim，使用一个进化的材料本构模型，从测量的边界载荷和变形提取不同的应力-应变状态。本构模型可以直接用于岩土工程问题的数值分析（例如有限元法）。拟议的研究将为快速，实用和更全面的土壤行为表征开辟新的和令人兴奋的大门。拟议的框架有可能改变岩土工程以外的材料测试和表征。该项目将支持研究生和本科生研究人员，并为未来的工程师提供培训。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The construction of any infrastructure on or within the ground will subject the surrounding soils to complex loading modes. In order to understand the short and long term behavior of an infrastructure element such as a building or a tunnel it is therefore essential to characterize the response of the surrounding soil. A soil material model that correctly captures soil behavior under general loading modes is requisite to solving such complex engineering problem known as a boundary value geotechnical engineering problems. Available laboratory tests are assumed to represent a single element and stress-strain path and do not cover the full range of loading paths experienced in a boundary value problem and is often insufficient to validate material model performance under general loading conditions.This research project will develop an integrated computational-experimental laboratory testing framework. Within this framework a laboratory test will be treated as a boundary value problem instead of a single element test. The test is coupled with an evolutionary inverse analysis approach that will allow for the extraction of multitudes of stress-strain paths generated within this boundary value problem. A soil-specific material constitutive model can be generated from this information. The test device is a modification of the widely used triaxial cell. The device includes lateral restraints in addition to frictional caps to induce non-uniform stress-strain states within the soil specimen. The device will be coupled with imaging techniques to capture the 3-D deformed shape of the specimen during loading. The novel inverse analysis algorithm, SelfSim, uses an evolutionary material constitutive model to extract the diverse stress-strain states from measured boundary loads and deformations. The constitutive model can be directly used within a numerical analysis (e.g. finite element method) of a geotechnical problem. The proposed research will open up new and exciting doors for fast, practical and more comprehensive soil behavior characterization. The proposed framework has the potential to transform material testing and characterization beyond geotechnical engineering. The project will support graduate and undergraduate researchers and will provide training to future engineers.