The impact of a PEER funded research project "A System-Level Study to Evaluate the Role of Soil Gradation on Seismically Induced Embankment Deformations" is highlighted below. The project Principal Investigator (PI) is Jason T. DeJong, Professor, UC Davis.
Industry NDA analyses to predict the seismic induced deformations are based, at its origin, on constitutive models developed for and calibrated to poorly graded sands. Knowledge on how soil properties and behaviors change with gradation is severely limited (even though gradation is always known), and hence routine practice defaults to the (incorrect) assumption that well graded soils behave similarly to poorly graded sands. The NSF leveraged results (in Project Image below) show that embankment deformations comprised of well graded soils can be 20% of poorly graded sands when subject to the same loading conditions. This implies that current industry practice may be excessively conservative. Large embankment dams routinely undergo re-evaluation, and due to recent increases in seismic hazard estimates, it often leads to remediation measures, typically at the cost of $50-$500M per embankment. If the project hypothesis is true, and well-graded soils deform only a fraction of poorly graded soils, retrofit measures may not be necessary or could be more modest in many cases, which could lead to significant savings for dam owners (and rate payers).