A comparison of two methods for measuring rigidity of saturated marine sediments.
Lasswell, James Bryan
Wilson, O.B. Jr.
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The results of two different methods for determining the rigidity modulus of a soft sediment are compared. In one method the resonant characteristics of a torsionally oscillating rod which are sensitive to the shear acoustic impedance of the sediment in which the rod is imbedded determine the complex rigidity. The second method utilizes the observation of the phase velocity of an interface wave at the water-sediment boundry. Shear wave speeds computed from the experimental data from both methods are quite similar in magnitude. For the sediment used here, the average value of shear wave speed determined from the interface wave experiment was 33 m/sec while the shear wave speed determined from the measured rigidity was 29 m/sec. The difference lies within experimental uncertainty. Trends in the mass-physical properties of the sediments are investigated by comparing graphically the dependence of both the real and imaginary parts of the complex rigidity on density, porosity, sound speed, silt and clay percentages, Poisson's ratio and density times sound speed squared.
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