Water content and Atterberg limits data are listed in Table 1. A more complete treatment of the water content results is presented in Winters (Chap. 41, this volume).
As expected, water content, wc, typically decrease with depth in Hole 995A, however, there are two exceptions. The Atterberg limits vary downhole also. The measured liquidity indices vary from 0.89 near the seafloor to 0.19 at 350.8 mbsf, and the plasticity indices range from 64 to 42.
General inferences about behavior can be made if values of plasticity index are plotted against the liquid limit on a plasticity chart (Fig. 2). Most of the sediment is expected to behave like an inorganic clay of high plasticity (above the A-line with a liquid limit greater than 50; Casagrande, 1947). One data point, which plots below the A-line, is indicative of inorganic silt with high compressibility. Data that defines a straight line that is parallel to the A-line is typical for sediment of similar geologic origin (Terzaghi and Peck, 1967). However, the data for this study is too limited to draw conclusions. The major clay mineral grouping can also be estimated from the plasticity chart (Holtz and Kovacs, 1981). Although most of the samples plot slightly further along the A-line than from previously published sources because of higher liquid limit and plasticity index values, the Atterberg limit results indicate that illite and kaolinite are the dominant clay mineral groups, not montmorillonite, which agrees with the mineralogical analyses performed on these samples (Winters, Chap. 41, this volume). However, the presence of high concentrations of biogenic material may cause this sediment to correlate poorly with standard empirical relationships.
The water contents of the entire consolidation test specimens typically were greater than shipboard values at the same sub-bottom depth. This may be the result of coring disturbance around the perimeter of the sample. At-sea water contents were obtained only from the center of the cores.
The shipboard vane-shear and pocket-penetrometer strengths, Su, were divided by the cumulative product of submerged unit weight, Ws, and sub-bottom depth, d, at most of the holes occupied during Leg 164 (Fig. 3) to produce a Su/(Wsd) ratio that can be used to qualitatively interpret stress history. The submerged unit weights were estimated from the shipboard grain density and water content data. Without exception, the Su/(Wsd) values are higher near the seafloor than at depth. Values range from a high of 46 in Hole 993A to a low of 0.02 in Hole 994C.
The adjacent vane-shear and pocket-penetrometer strengths that were performed at the same depth on the whole-round core sections near the consolidation samples from Hole 995A agreed remarkably well with each other (Table 1). The sensitivity, St = intact vane shear strength/remolded vane shear strength, values indicate that the sediment classifies as "sensitive" (Bowles, 1979). Because the same magnitude of sensitivity was present both in sediment obtained with the APC (Advanced Piston Core) and the XCB (rotary Extended Core Barrel), it appears that rotary coring did not appreciably disturb the uppermost sample in Hole 995A obtained with that device.
Constant-rate-of-strain
consolidation tests were performed to evaluate the stress history of the
sediment (Table 2, Fig.
4). The test results are plotted as void ratio, e = volume of
voids/volume of solids, vs. the logarithm of the vertical effective stress, 
'v.
Typical e - log'v
curves form a straight line, the virgin compression line, at higher stresses.
The slope of the virgin line is termed the compression index, Cc, and
represents how much one-dimensional compression can be expected from a
logarithmic cycle of loading.
The preconsolidation
stress, P'c,
can be determined from consolidation test results that have a straight virgin
line by the Casagrande (1936) graphical technique and is assumed to equal the in
situ maximum past stress, 'vm.
The consolidation results exhibit a wide range of maximum past stresses and
compression indices. Maximum past stresses vary from 40 kPa to 2730 kPa at
depth. The compression indices change by a magnitude of 2 and are 5% to 43%
higher than what would be expected from an empirical relation based on the
liquid limit results (Terzaghi and Peck, 1967). However, the high biogenic
content of the sediment may affect empirical comparisons.
