Physical Properties Of Marine Sediments And Its Applicability In The Solution Of Engineering And Environmental Problems

For the present study four different physical properties were investigated: the velocity and the attenuation of Pand<br>S- waves, the electrical resistivity and the natural gamma radioactivity. In addition, eight sedimentological<br>parameters were used for correlations: sand, silt and clay contents, wet bulk density, porosity, water content,<br>shear strength and C/P ratio (the ratio between the shear strength and the overburden pressure).<br>The results show that no technique used alone, can provide unequivocal evidence about the sediment<br>characteristics. Some techniques respond primarily to lithology, some to porosity and density, and others to<br>pore fluid chemistry. The velocity of shear waves, correlate very well with parameters relevant to engineering<br>problems such as wet bulk density, porosity and shear strength. In addition, the velocity ratio Vp/Vs,<br>traditionally used as a lithology indicator (Hamilton, 1979), gives no conclusive information about the kind of<br>sediment. The attenuation seems to be insensitive to changes in the sedimentological parameters. The electrical<br>resistivity appears to be more suitable for the evaluation of environmental than of engineering parameters. The<br>absence of correlation between the coefficient of electrical anisotropy and shear strength indicates that the<br>electrical resistivity is less sensitive to localised variabilities in the packing configuration. The natural gamma<br>radioactivity shows the best correlation with parameters such as wet bulk density and shear strength. The<br>method is very sensitive to small changes in the sedimentological characteristics of the sediment.<br>Moreover, the applicability of the physical models used to the characterisation of deeep sediments can not be<br>used without making adjustments to constants or exponents, or introducing compensations.