Buffington, Hamilton, and Moore 



DIRECT MEASUREMENT OF SEA-FLOOR SHEAR STRENGTH 



The response of sea-floor sediment to imposed loads and struc- 

 tures is becoming increasingly important to the U. S. Navy and other 

 organizations considering sea-floor installations. The measurement 

 of shear strength is, therefore, of special concern. This can be 

 done from remotely collected samples if they are undisturbed and if 

 the validity of the measurement can be established. 



To this end a carefully controlled experiment, to compare 

 in situ and laboratory vane-shear strengths of marine sediment, was 

 carried out in October 1966 from DEEPSTAR 4000. The tests util- 

 ized a NEL-developed vane-shear strength machine, designed for 

 operation from deep diving vehicles. This machine was mounted as 

 a unit including two adjacent core tubes (Fig. 6) for simultaneous 

 collection of in situ strength data and sediment for later laboratory 

 study. The experiment was accomplished off San Diego, California 

 at a water depth of 365 meters in an olive gray, clayey silt. 



Fig. 6 - Vane-shear machine 

 adapted for use with DEEP- 

 STAR 4000. The white strip 

 below the housing protecting 

 the vane in the center is 12 

 inches long. 



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