IN-SITU STRENGTH OF SEAFLOOR SOIL DETERMINED FROM TESTS ON PARTIALLY 

 DISTURBED CORES 



Technical Note N-1295 



YF38. 535.002.01.013 



by 



H. J. Lee 



ABSTRACT 



The major obstacle to rational design of seafloor foundations and 

 anchors has been a lack of good quality information on the bottom 

 sediment engineering properties . Considerable engineering property 

 data have been obtained through laboratory testing of core samples, 

 but most of these data are of questionable validity because of the 

 sample disturbance factor. To improve the usability and credibility 

 of laboratory test data, an experimental investigation was undertaken 

 to determine the extent of disturbance involved in seafloor soil 

 sampling and handling. In-situ tests were performed and related to 

 comparable laboratory tests. The soils tested were from the Santa 

 Barbara Channel with a terrigenous (land-derived) origin. A technique 

 based on earlier work was developed for predicting in-situ shear 

 strength on the basis of laboratory test results. Various disturbance 

 mechanisms including sampling, vibration, long-term nonref rigerated 

 storage, and water and air expansion were investigated and analyzed 

 quantitatively. Strength reductions varying between 15 and 50 percent 

 were observed to result from these disturbances. The in-situ strength 

 prediction procedure appears to be capable of compensating for all 

 forms of disturbance except for those developing as a result of gas 

 expansion. 



Approved for public release; distribution unlimited. 



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