The impact of a PEER funded research project "DEM Modeling of the Influence of Depositional Fabric on the Mechanical Properties of Granular Sediments using XRT Data" is highlighted below. The project Principal Investigator (PI) is Nicholas Sitar, Edward G. Cahill and John R. Cahill Professor, UC Berkeley. The research team includes Fernando Estefan T. Garcia, Post-doctoral student, UC Berkeley.
This research effort represents initial investment in a major research thrust to accurately characterize the fabric of natural deposits and to use these results to develop mechanistic based models of granular deposits using massively parallel DEM codes. Specifically, the role of depositional environment is currently not being taken into account in typical field characterization of potentially liquefiable deposits even though the differences in observed site response due to the different origin of the materials have been addressed extensively in recent research. Similarly, due to the lack of data, to-date the natural fabric of the granular deposits, sands in this case, has not been modeled either by DEM or by using an appropriately configured constitutive model using continuum representations, e.g. finite element method (FEM) or material point method (MPM). Our preliminary results from trial scans show that due to the intimate contact and packing of particles, naturally deposited sands exhibit much high mobilized friction angle at low confining pressures than either hydraulic fill or pluviated samples used in most of the studies to date. We expect that our work will show that there is a significant difference between reconstituted and naturally occurring deposits that has a significant impact on their behavior under both static and cyclic loading. Most importantly, the results of the experimental work will allow the development of higher fidelity representations in DEM simulations and allow for development of more accurate and representative parameters for constitutive models used in continuum simulations.
Firgure 1. X-Ray Tomography Scans of Fine Sand Fabric