Yield strength determination from slump test

ABSTRACT The routinely determination of the yield strength of muddy beds is particularly important for the assessment of navigation in ports located in estuaries where cohesive sediments are abundant. The use of the nautical bottom concept may allow for a significant increase of the navigation depth. Sediments mixtures rich in clay and silt could behave as either a solid or a fluid depending on the forces acting on them. A concentrated mud sample will retain its shape if subject to shear stresses bellow the yield strength. However, if the same sample is subject to shear stresses above the yield strength, it will flow. One simple way of determining the yield strength is by performing a slump test. In this work, instead of just measuring the deposit final height or radius, as it has been done in the past, we fit an analytical expression to the deposit final geometry to estimate the yield strength. Simultaneous yield strength measurements using a conventional vane rheometer showed to be in very good agreement with the proposed technique independently of the mud sample origin, which is a clear improvement over the existing slump test methods, which just use the final height of the deposit.