the calcareous ooze material undergoes a less ^han -average magnitude 

 of secondary consolidation, compared to terrestrial fine-grained 

 soils in general. The secondary consolidation behavior of this 

 sediment and the causes for this behavior are the subject of continuing 

 study. 



Artificial Soil Test Results 



As indicated earlier, difficulty was experienced in identifying 

 grain crushing in the first two consolidation tests on natural 

 samples. Grain size determination results before and after loading 

 to 1,530 kPa (32,000 psf) suggested no significant changes had 

 occurred. Visual examination revealed holes punched in many test 

 walls both before and after consolidation testing, making an assessment 

 as to the effect of consolidation on test integrity very difficult 

 to substantiate. It was hypothesized that the fine-grained fraction 

 of the ooze material was acting as a load distributor, evenly stressing 

 the tests so as to limit crushing. To test this hypothesis, an 

 artificial sample, with all material passing the No. 325 sieve 

 removed, was consolidation tested as above. 



Specimen Preparation. The test sample was prepared by first 

 dispersing material from Box Core 4, to 76mm increment (0 to 

 3 in.), using distilled water and sodium pyrophosphate. This material 

 was then washed on a 325 sieve using distilled water, while avoiding 

 unnecessary abrasion of the material. (The resulting material, 

 with fines removed, had a specific gravity of 2.79. The specific 

 gravity of calcite is 2.93 and that of aragonite is 2.71 [39].) 

 At the conclusion of washing, the retained material was placed 

 in a beaker of seawater. The seawater "saturated material was then, 

 after a period of equilibrating, spooned into the consolidometer 

 ring of the Karol-Warner unit and then struck off even with the 

 top edge. 



Grain Crushing . The e-log o^ curve resulting has been plotted 



in Figure 12, labeled "artificial.'' The start of the very steep 



curve is believed to mark the start of significant grain crushing; 



i.e., between 50 and 200 kPa (about 1,000 and 4,000 psf). The artificial 



specimen was loaded to 2,420 kPa (50,600 psf) with the test results 



indicating a C of 1.868 and a C of 0.030. The results of grain 



c s 



size analyses on the 1 -D compression specimen after testing and 



on the excess sample (which is considered representative of the 



specimen initial state) are presented in Figure 13. The grain size 



curves confirm that test crushing did occur in the artificial sample 



under consolidation. Most crushing occurred in the medium sand 



size fraction, with 30% of the material being reduced to a size 



passing the 325 sieve. The results of this third consolidation 



test confirm the role of the fine-grained fraction in this particular 



11 



