Appendix A 

 FY-71 LABORATORY TESTS 



GENERAL 



Small-scale model immediate and long-term breakout tests were 

 performed in the NCEL Seafloor Soils Laboratory in FY-71 . The tests were 

 initiated specifically to investigate the breakout of objects of very shallow 

 embedment for application to the various NCEL programs which involve 

 bottom-sitting devices. In addition, however, a number of tests with some- 

 what greater embedment depths were performed in order to allow comparison 

 with earlier NCEL tests and to provide additional, well-controlled test data on 

 the general problem of partially embedded object breakout. 



In all, about 90 tests were performed. Of these, 40 were classed as 

 immediate breakout tests, in which upward loads on embedded objects were 

 increased rapidly to breakout. The remainder were long-term breakout tests. 

 A fraction of the immediate force was applied and the time required for break- 

 out was measured. 



EQUIPMENT 



Simple experimental equipment was used so that a large number of 

 tests could be performed economically. The equipment consisted of two 

 55-gallon oil drums on which were mounted knife-edges for use as fulcrums 

 to levers. The levers were solid steel bars, 4 feet long, with mercury switches 

 mounted near their centers. The drums were partially filled with a cohesive 

 soil into which objects were embedded. Lines were attached from the objects 

 to the inner ends of the levers. At the other ends of the levers were placed 

 weight stands on which weights were added to provide the required upward 

 line forces to the embedded objects. The mercury switches were wired into 

 circuits containing electric clocks. When breakout occurred and the levers 

 deflected, the mercury switches opened, thereby stopping the clocks. It was 

 not necessary, therefore, to observe the tests continuously. A diagram of the 

 testing configuration is shown in Figure A-1 . 



It was felt that the soil shear strength would become a critical parameter 

 during the data analysis phase. Therefore, special attention was given to devel- 

 oping a simple and accurate device for measuring the in-situ strength of the soil 

 within the drums. A hand-held device was developed which consisted of a 1 .4- 

 inch-diameter, 1 .4-inch-long, four-biaded vane mounted on a 24-inch aluminum 



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