This award supports a joint research project between Dr. Alaa Ashmawy, Department of Civil and Environmental Engineering, University of South Florida (USF), Tampa, Florida and Dr. Ahmed Abdel-Rahman, Civil Engineering Department, the National Research Center (NRC), Cairo, Egypt. They propose to investigate the physical and numerical modeling of geogrid-soil cyclic interaction. The use of geogrids as mechanical inclusions in earth construction has been on the rise in both the US and Egypt. However, the interaction mechanisms between granular soils and geogrids are not yet fully understood, especially under cyclic loading conditions such as traffic and earthquake loading. In an earlier project, the principal investigators designed and manufactured a new multi-purpose geosynthetic testing apparatus capable of performing pullout and direct shear testing on soil-geogrid interfaces. The PIs plan to utilize the new apparatus, currently housed at the NRC in Cairo, to investigate the cyclic interaction between granular soils and geogrid inclusions. The Egyptian team will carry out a comprehensive experimental program to examine the dependence of static and cyclic pullout strength on geogrid opening dimensions in relation to grain size. The team at USF will conduct numerical modeling of the micromechanics of the system using the Discrete Element Method (DEM) to verify and calibrate the experimental data. Modifications to the current reinforced earth design and geogrid manufacturing standards will be proposed accordingly.
Scope: The PI has recently developed a new technique for numerical modeling of angular particles using the DEM method. This planned research activity will allow validation and improvement of the technique through comparison with experimental data collected by the Egyptian team. The NRC in Cairo possesses the necessary infrastructure for the experimental study, and the DEM software, algorithms, and numerical research tools are available at the USF. The findings are expected to advance the state of knowledge with respect to geosynthetic-soil interaction as well as discrete element modeling of reinforced granular soil systems. The project will involve an American graduate student who will have a unique learning opportunity through her visit to and work at the cooperating scientist's laboratory in Cairo. An undergraduate student working on the project will also be supported through a REU program at the USF's College of Engineering. Both students are members of underrepresented groups. Broad dissemination of research findings will be done through publication in journals, conference proceedings, and the Internet.
