Geotechnical properties of deep continental margin soils

Abstract

The engineering properties of deep continental margin sediments were determined on a worldwide basis. Deep Sea Drilling Project (DSDP) core data and material were utilized from over 900 cores obtained from 89 sites, primarily on the continental margins. Cores were recovered from penetrations to 200 m in water depths averaging 3000 m. Supplementary laboratory testing on selected cores was directed toward determining index properties and shear strength properties of the sediments. The study included a literature review of deep-sea soil properties, the results of which are to be used by DSDP to evaluate foundation conditions for reentry cones with long casing strings. The results will also be used for a feasibility study of an ultradeepwater marine riser and wellcontrol system. The marine sediments examined can be divided into three main types: clay, calcareous ooze, and siliceous ooze. Sediment distribution consisted of 48% calcareous ooze, 43% clay, 6% siliceous ooze, and 3% volcanic ash. Because of the sample disturbance inherent in the deepwater coring operation, emphasis was placed on analyzing sediment properties not significantly affected by changes in in situ stresses and structure caused by sampling. Averages and ranges in values of water content and unit weight are presented for the three main sediment types. Plasticity and strength characteristics are discussed in detail and the elastic and compression properties are outlined. The geotechnical properties of deep continental margin soils are summarized.

Mass transport in Eocene pelagic chalk on the northwestern edge of the Arabian platform, Shefela area, Israel

“…DSDP reports have frequently referred to mechanical behaviour of pelagic carbonates through the various stages of diagenesis (Davie, Fenske & Serocki, 1978;Demars, 1981 ;Garrison, 1981), though slope failure in recent pelagic ooze in deep ocean basins has not been documented. Calcareous pelagic oozes should resist failure because of their relatively high internal friction angle (Demarset al, 1976;Davie et al, 1978), their reduced plasticity when compared to clays, and the slow rate of deposition which allows gradual consolidation and release of pore fluids, eliminating build-up of pore pressure which may contribute to failure (Morgenstern, 1967). Nevertheless, under special circumstances, mechanical stability of calcareous oozes may be drastically reduced.…”

Upper Campanian suspected silicified seismite related to the Syrian Arc tectonic system in the Middle East

“…They suggested that low-density of the siliceous sediment layer result in gravitational instability with the overlying non-siliceous unconsolidated sediments (density inversion). However, the bulk density values presented by Davie et al (1978) relate to sediment dominated by radiolarian and diatomaceous opaline tests. These form a highly porous network providing large space for interstitial seawater, and hence a sediment with a low bulk density.…”

“…As a result of these puzzling controversial affinities the petrography and geochemistry, these chert beds were intensively studied and several theories were suggested for the formation of this variety of siliceous lithologies and structures. Davie et al (1978;in Fink and Reches, 1983a, p. 268) examined the geotechnical properties of unconsolidated marine sediments in DSDP cores and found that siliceous sediments have more than twice the water content and hence lower bulk density (1.35 g/cm 3 ) than calcareous (1.60 g/cm 3 ) and clayey (1.54 g/cm 3 ) sediments. Fink and Reches (1983a) applied these bulk density figures to the initial Mishash Formation sediments.…”

Water Content and Atterberg Limits of Sediments at Deep Sea Drilling Project Holes 417A and 418A, Legs 51 and 52, West Atlantic Ocean

“…At all burial depths, the liquid limit is appreciably higher than the water content, which is reflected in the unusually Davie et al (1978).…”

“…ically organic sediments below. Figure 2, adapted from Deep Sea Drilling Project Technical Report 9 (1976) by Davie et al (1978), also shows numerous other data. The clay from Site 302, which has similar properties to the data presented in this paper, is from the Sea of Japan (Leg 31).…”