Index properties of sediments from ODP Hole 101-630B (Table 2)

Three holes were cored at Site 630 during Leg 101 of the Ocean Drilling Program. Whole-round samples were obtained for geotechnical analyses from Hole 630B. Consolidation studies, which relate changes in the coefficients of consolidation, compressibility, and permeability to the overburden pressure, indicate that sediments recovered to 79.4 mbsf (meters below seafloor) are not significantly consolidated. This may be a function of total carbonate content, mineralogy, and type of carbonate constituents. The lower total porosity and permeability of Section 101-630B-2H-5 relative to 101-630B-5H-6 and 101-630B-9H-6 are explained in terms of effective fluid flow, total calcium carbonate content, and type of constituents present.Results from triaxial shear testing and direct shear testing indicate that Section 101-630B-2H-5 has a higher degree of cohesion and a higher angle of internal friction (0) than sediment recovered deeper in the section, although angles of internal friction from all three samples are lower than typical angles measured from deep-sea foraminiferal ooze. Attempts to compare triaxial shear results qualitatively with measurements of undrained vane shear strength from Hole 630A suggest that the latter may be meaningless if taken from sediments dependent on overburden pressure to maintain strength.Calculations based on consolidated and drained shear strength suggest that if the sediment column is homogeneous, the slope will be stable to 14° of inclination. If the inhomogeneities in the section, such as the turbidite layers known to be present, are weaker than the sediments tested, then the stable slope inclination may be less than that calculated. This is substantiated by the abundance of seismic evidence for slumping, sliding, and imbricate thrusting on this gentle (2°-3°) slope.