Investigations of deep-sea sediment cores

Abstract

Thirty-five gravity-and piston-type cores were collected by the Hydrographic Office in depths of 400 to 5120 m from 8 different areas in the North Atlantic, Central Pacific, and West Mediterranean Sea. Most cores were composed of terrigenous silt-and clay-size particles. Mass physical property laboratory measurements of more than 700 samples included: grain size, specific gravity of solids, wet unit weight, water content, void ratio, pore-water saturation, liquid and plastic limits, and compressive and/or vane shear strength. Also computed were porosity, liquidity index, plastic index, cohesion, sensitivity, activity, and modulus of elasticity.

Organic matter and the geotechnical properties of submarine sediments

“…As will be shown in the following discussion, these organic-rich deposits display distinct geotechnical properties and stability characteristics in contrast to the other Peruvian margin deposits. Geotechnical properties, such as wet bulk density, water content, and Atterberg limits, discussed in the following section, were determined using the procedures outlined by Richards [8]. Shearing strengths were measured with a laboratory vane shear apparatus using a vane rotation rate of 60 degrees per minute.…”

Site 743

“…At the present stage, however, the sparse data coverages indicate no overconsolidation indicative of large-scale erosion or slumps removing extensive sediment masses in the drilled sequence. Skempton (1970) established that the ratio of shear strength to effective overburden pressure, as calculated by Richards (1962), ranges between 0.2 and 0.5 in normally consolidated marine clays. Although this relationship may not be exactly the same for the more unsorted sediments present at Site 743, a rough estimate of effective overburden shows that even taking the highest of the fall cone-measured shear strength values, the drilled sequence does not seem to be over consolidated.…”

Estimation of the oriental shear strength of deep sea sediments from engineering index properties

“…Water content has long been recognized as one of the major factors which affect the shear strength of sediments (Richards, 1962). Trask and Rolston (1950) show that an inverse relationship exists (for specific grain size groups) between water content and the logarithm of shear strength of the San Francisco Bay sediments.…”

“…This assumption is based on only a limited amount of research conducted on this subject (Casagrande, 1932;Winslow and Gates, 1963 Richards (1962) and Keller (1964), and from the National Oceanographic Data Center. GENERAL Tables II, III In order to give a more complete picture of the ranges and statistical parameters of each of the engineering properties analyzed, Table V and Fig-ure 10 through Figure 15 were prepared.…”