Test 4. The test was performed to define the failure envelope in 

 a clearly normally consolidated region. 



Test 5. The test was performed to determine the influence of K Q 

 consolidation on strength properties. 



The primary objective of the triaxial testing was to develop an 

 estimate of the strength distribution in these pelagic clays to a 

 significant sub-bottom depth (100 ft) . Since drained and undrained 

 failure envelopes generally correspond (Lambe and Whitman, 1969, p. 427) 

 if effective stresses are used, the parameters c and <j> derived above 

 can be used directly in a limiting equilibrium problem. Long-term or 

 drained anchor holding capacity and foundation bearing capacity can be 

 readily calculated using existing procedures (e.g., Taylor and Lee, 

 1973). Obtaining an undrained strength distribution for analysis of 

 short-term capacity is somewhat more difficult. The stress paths of 

 Figure 8 can be used as a starting point since they determine several 

 different undrained shear strengths resulting from different initial 

 consolidation conditions. However, there are two problems: (1) the 

 initial conditions of the four isotropically consolidated samples do 

 not correspond to the anisotropic consolidation conditions in-situ and 

 (2) the strengths correspond to discrete situations; a means for inter w 

 polating between the situations is needed. 



The problem of K consolidation is approached by observing the re- 

 sults of Tests 4 and 5. Both involve the same order of magnitude of 

 stresses but Test 4 was consolidated isotropically while Test 5 was 

 consolidated under K conditions. It may be seen that the shapes of 

 the curves as they approach the failure envelopes are similar. A means 

 of using this similarity has been suggested previously (Taylor, 1948, 

 p. 383) : A point is located on a stress path resulting from isotropic 

 consolidation which has the same stress conditions as would result from 

 K consolidation. That is, Oo is equal to K a-^. The stress path which 

 would result from K Q consolidation is assumed to be identical to the 

 portion of the stress path resulting from isotropic consolidation be- 

 tween that point and the failure envelope. This procedure has been 

 criticized (Ladd, 1965) because the paths are not usually identical. 

 For the purposes of this report, the similarity between the two paths 

 appears good enough to assume that they are identical. 



To use the Taylor (1948) technique it is necessary to have an esti- 

 mate of the parameter K Q for a variety of stresses. The value of K Q 

 obtained from the one anisotropic consolidation test was 0.52, and will 

 be assumed to apply to the entire range of stress. This may be a poor 

 assumption for the low stress region; however, trials of other values 

 did not significantly alter the resulting strength distribution. A 

 plot of the line representing K Q equal to 0.52 is given on Figure 8. 



The stress paths of interest are those above the K Q line in 

 Figure 8. It is possible to interpolate between these paths by using 

 a modified version of an equation given by Ladd (1965) : 



19 



