Dynamic Properties of Some Eastern Mediterranean Marine Sediments

摘要

A series of resonant column tests on sediments from offshore Haifa, Israel are presented in this paper. Samples were obtained from both the Akhziv submarine canyon and the undisturbed slope located on the continental terrace of Northern Israel in the Eastern Mediterranean using a gravity corer in 59 to 699 m of water depth. The continental shelf of northern Sinai, Israel, and Lebanon is made of 1-2-km-thick Nile-derived sediments of the Pliocene-Quaternary age that were transported to the northeast by the counterclockwise contour current system of the Southeastern Mediterranean Sea, and accumulated along the continental margin. The sediments tested consist of dark grey silty clays (MH/ CH). The sedimentological pattern over the continental shelf and the adjacent parts of the deep-sea Levant Platform essentially consists of continuous hemipelagic sedimentation of the Nile-derived sediments along the continental margin and frequent episodic earthquake triggered sediment slumping with redistribution down slope. The soft sediments described in this paper were trimmed for use in the resonant column apparatus using an osmotic knife in the shape of a split mold. The resonant column utilized in this study was a fixed free apparatus. The total unit weight of the specimens ranged from 14.31 to 17.98 kN/m~3, whereas the water content varied from 40 % to 95 %. Maximum shear modulus varied with depth of water, location on the shelf and in the canyon. For the undisturbed slope, the maximum shear modulus is approximately 25 to 29MPa. For the canyon flank, the modulus ranged from 4.2 to 17.2 MPa. This is in contrast to the canyon bed where shear modulus ranged from 220 to 334 MPa. The increase in shear modulus of the canyon bed sediments is believed a result of either or both internal structure or slight cementation in the Akhziv material based on a combination of previous triaxial testing and site geology. The corresponding damping ratio ranges from 0.5 % to 4 % as a function of shear strain and effective stress. Modulus and damping test results are compared with other marine sediments: offshore Eureka, CA; Navarin Basin, Bering Sea; Gulf of Mexico; and Casablanca and the Santa Barbara Channel California.