Investigation of the viscoelastic properties of a water-saturated sediment.

Abstract

Experiments were made in the laboratory to determine the feasibility of adapting to the measurement of the shear elastic properties of sediment- like materials techniques already proven for use on viscoelastic liquids. A torsional transducer attached to an aluminum rod was immersed in a Kaolin sediment and driven in either a pulse-echo mode or a standing wave mode. Both techniques were found to be satisfactory and in good agreement over the limited frequency range (38 to 39 kHz) imposed by the characteristics of the transducer-rod combination. In the pulsed mode, measurement of the changes in attenuation and phase of the pulses (tone-bursts) in the rod when the rod is immersed in the sediment allow calculation of the real and imaginary parts of the complex shear modulus. In the resonant mode, measurement of the changes in resonant frequency and the electrical resistance at resonance upon immersion allow a similar calculation of the complex shear modulus. It was found that a complex shear modulus did exist for the sediment investigated, thus indicating that the sediment displays both viscous and elastic properties. Furthermore, the measured properties were found to be a sensitive function of sediment compaction.