INTRODUCTION 



This report is the second of a series dealing with engineering 

 properties of seafloor soils on a worldwide basis, the first report 

 having dealt with Bering Sea and North Pacific Ocean soils (Lee, 1973a). 

 In this series the major deep ocean soil types (calcareous ooze, 

 diatomaceous ooze, radiolarian ooze, and pelagic clay) will be sampled 

 and estimates of in-situ engineering behavior will be made, primarily 

 on the basis of laboratory test results. Reports will be prepared 

 periodically as sets of tests on particular soil types are completed. 

 Ultimately a final report summarizing these reports and directed toward 

 practical engineering problems will be prepared. It will include 

 general correlations of engineering properties with either soil type 

 or soil index properties for the various materials found in the world's 

 oceans . 



This report includes the results of tests which were performed on 

 two high quality box core samples obtained from the Pacific Ocean be- 

 tween Hawaii and California. The locations of the cores are proprietary; 

 however, the water depth in this general region averages about 15,000 

 feet. The sampling device was a spade- type box corer developed at the 

 Scripps Institution of Oceanography with the support of the Navy Elec- 

 tronics Laboratory (Rosfelder and Marshall, 1967). The cores measured 

 8 inches by 12 inches in cross section and were about 20 inches long. 

 The length to width ratio of 2.5 is excellent in terms of reducing 

 disturbance (Hvorslev, 1948). The cores are identified as Box A and B. 



The two cores contained a typical deep ocean soil, pelagic clay 

 (often referred to as "red clay" in the literature) . This material is 

 known to cover about 40 million square miles (or about 33 percent) of 

 the seafloor. It is usually brown in color and contains very fine 

 grained material, much of which is thought to be wind-borne dust and 

 volcanic ash. Organic material with the exception of such items as 

 shark's teeth is missing. The clay accumulated very slowly (about 1 to 

 2 mm per 1,000 years) and often contains manganese nodules. A map 

 illustrating locations where pelagic clay is found is given in Figure 1. 



The samples were subjected to vane shear and water content testing 

 upon their arrival at NCEL (less than one week after being taken from 

 the seafloor). About ten 2.5-in. diameter cores were cut from the box 

 cores and sealed for later triaxial and consolidation testing. 



PROCEDURES 



Accepted procedures (Lambe, 1951) were followed in the performance 

 of index property testing. Consolidation tests were conducted in either 

 an Anteus back-pressure consolidometer or the NCEL Specially-Developed 

 Low Pressure (SDLP) consolidometer (Herrmann and others, 1972). Tri- 

 axial testing was conducted using a system assembled at NCEL for test- 

 ing seafloor soils. Samnles were back-pressured with seawater using a 



