Geotechnical properties and behavior of high-porosity, organic-rich sediments in Eckernforde Bay, Germany
Date of Original Version
The organically rich, fine-grained, very soft, high porosity sediments in the inner portion of Eckernforde Bay, Germany have varying amounts of methane gas, with the horizon of gas fluctuating vertically on a seasonal cycle. The sharp vertical gradient in water content, with values exceeding 500% at the sediment-water interface, and corresponding gradient in density can be expected to cause a significant subbottom acoustic impedance contrast in these surficial sediments. Equations are presented to characterize geotechnical property variations of the upper 5 m. The upper 1.5 m exhibits appreciable 'apparent' overconsolidation with a trend toward a normally consolidated stress state at 2.5 m depth. The coefficient of permeability of the upper 40 cm is low (4 x 10-6 cm s-1) and the sediment is highly compressible with compression indices of 2.7-6.8. Triaxial compression test results indicate that the sediment behaves as a normally consolidated clay with a low friction angle (22°). The rheological behavior of the upper 20-30 cm, determined with a small vane device, is indicative of a shear-thinning material, implying that the resistance to penetration decreases with increasing velocity.
Publication Title, e.g., Journal
Continental Shelf Research
Silva, A. J., and H. G. Brandes. "Geotechnical properties and behavior of high-porosity, organic-rich sediments in Eckernforde Bay, Germany." Continental Shelf Research 18, 14-15 (1998): 1917-1938. doi: 10.1016/S0278-4343(98)00063-6.