ENGINEERING PROPERTIES OF A PELAGIC CLAY 

 Technical Note N-1296 

 YF53. 535. 002. 01.013 



by 



H. J. Lee 



ABSTRACT 



Pelagic clay is a common ocean soil type covering over 30 percent 

 of the seafloor. Two high quality box core samples of pelagic clay 

 were obtained and subjected to index and engineering property testing. 

 The results of tests on both cores were similar indicating little areal 

 variability. The shear strength near the soil-water interface was 

 about 1 psi, a relatively high value, and the soil was found to be 

 virtually incompressible up to a compressive stress of about 4 psi. 

 When remolded, the strength of the soil was significantly decreased, by 

 as much as a factor of 6. The soil was also found to be very compres- 

 sible beyond a stress of 4 psi. A technique was developed for using 

 triaxial test results to derive shear strengths below the level of 

 sampling. The resulting strength profile indicates a very gradual in- 

 crease of strength with depth. Implications regarding the use of direct 

 embedment anchors are discussed. 



Approved for public release; distribution unlimited. 



