A discussion of possible measurement techniques for muddy sediments and of the related modeling challenges

Abstract

Present paper draws on recent work of the late William Carey at Dodge Pond, CT, and on related modeling efforts at RPI. Carey affirmed that muddly sediments can have a substantial air bubble content. The water, solid particles (clay), and bubbles lead to a low sound speed that for low frequencies is explained by a modification of the Mallock-Wood formula. Independent measurements of mass density and sound speed should enable estimates of the fractional composition. The attenuation of sound in muddy sediments without bubbles is small, much smaller than of sandy sediments, and this is explained in terms of the card house model because of the very small size of the clay particles. The larger bubbles are randomly dispersed and have flattened shapes (also explained by the card-house model), and lead to scattering and reflection phenomena. Speculations are made as to whether inversion techniques can be devised to determine bubble shapes and size distributions. The small shear modulus of muddy segments has been tentatively explained in terms of electrostatic effects inherent to the card-house model, and this can possibly be measured by interface waves. Paper also suggests that penetrometer measurements, guided by theoretical modeling, may lead to useful inferences.