Since there were no residual pore pressures, the sample disturbance 

 correction procedures of Lee (1973a) could not be applied. Instead the 

 procedures of Lee (1973b), which are based on Ladd and Lambe (1963), 

 were used. These procedures involve the application of relatively large 

 consolidation stresses (i.e., well above the in-place overburden pres- 

 sures) in the triaxial cell. Basic stress path parameters (Skempton's 

 parameter, A, and c and <j)) are obtained. The strength of the sample 

 under the correct in-place overburden pressure is calculated (using an 

 equation given by Lee, 1973b). Most of the effects of sample disturbance 

 are corrected for in this manner. This procedure can also be used to 

 obtain estimated strength profiles for the sediment below the level of 

 sampling. To do this, it must be assumed that the type of sediment does 

 not change greatly below the level of sampling. 



Estimated undisturbed undrained shear strength profiles were devel- 

 oped in this manner for the sediments at each of the three sites. These 

 are given in Figures 7, 8, and 9 along with the measured in-place strengths 

 and the measured, uncorrected laboratory vane strengths. Discussions of 

 the characteristics of the data from each of the sites are given below. 



Site I (pelagic clay) 



No in-place vane shear tests were conducted at Site I because of 

 the great water depth. The strength profile estimated from triaxial 

 tests is almost identical to that developed for a Pacific Ocean pelagic 

 clay (Lee, 1973b). The miniature vane strengths are smaller, by almost 

 50%, than the estimated profile. This is probably a result of sample 

 disturbance, which is corrected for in the triaxial test profile. 

 However, since no in-place measurements were made, it is impossible to 

 determine whether the estimated profile is actually correct. Direct in- 

 place strength measurements will be made in a pelagic clay this fiscal 

 year (DOSIST III) so that a determination of the best means of sample 

 disturbance correction can be made. 



Site III (globigerina ooze) 



Calcareous oozes often contain the relatively large (fine sand 

 size) tests of globular foraminifera, the much smaller tests of nannofos- 

 sils, and often a good deal of clay. The engineering behavior of the 

 sediment appears to be strongly related to the relative proportions of 

 these materials. If the percentage of fines is high (as was the case 

 with the sediment tested by Valent, 1974), the behavior is similar to 

 that of a silty clay. If the percentage of foraminifera (globigerina) 

 is high enough, the behavior is quite different. The forams form an 

 open framework, and the fines only partially fill the interstices. 

 Overburden stresses are carried by the forams, and the fines do not 

 consolidate until the stresses become large enough to crush the forams. 

 Virtually no cohesion develops. When the material is sampled and over- 

 burden stresses are removed, it takes on the consistency of partially 

 melted ice cream. 



11 



