Sedimentary and geo-mechanical properties of Willapa Bay tidal flats

abstract The mechanical and physical properties of sediments from a tidal channel and adjacent flats weremeasured in Willapa Bay, Washington State, USA. Yield strength, Young’s modulus, and tensile fracturetoughness measurements revealed seasonal changes in the behavior of these tidally influencedsediments. In summer, both flats and channel sediment behaviors were similar, while during winter,channel sediments were much weaker than sediments on the flats. Sediments typically displayed anincreasingly elastic and fracture behavior with depth below the surface, with the exception of winterchannel deposits, which deformed viscously. Porosity was inversely correlated to the measuredgeotechnical properties, resulting in increased strength with depth. In addition, each mechanicalproperty was linearly proportional to one another. Average grain size did not differ within the field site,eliminating any effect that changing grain size might have on the mechanical behavior and strength.Overall, compressive and tensile strengths were low in shallow Willapa Bay sediments (o20 cm).& 2012 Elsevier Ltd. All rights reserved.