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.
