Also during the second year of the program, a computer model based 

 on elastoplastic theory was developed for analyzing the breakout problem. 

 The model was formulated in such a way that the force required for essentially 

 instantaneous breakout could be related to the object geometry, embedment 

 depth, and soil shear strength. No time characteristics were considered.^ 



During the third and final year of the DSSP breakout program, field 

 tests were conducted in 100 feet of water off the Louisiana coast in the Gulf 

 of Mexico. The same objects used in the San Francisco Bay tests were partially 

 embedded in the bottom soil and then removed by using inflated pontoons to 

 provide the required forces. The upward displacements of the objects as func- 

 tions of time after force application were measured in several of the tests.' 



During the latter portion of the third year of the program, small-scale 

 laboratory tests were conducted at NCEL. These involved placing small objects 

 in a tank containing disturbed cohesive soil obtained from nearby marsh areas. 

 An uplift force was applied, and the total time required for breakout was mea- 

 sured. Intermediate object displacements were not measured.' 



After the experimental testing, a report describing the tests and list- 

 ing the test results was prepared.' This report included an empirical equation 

 relating breakout force, breakout time, object geometry, soil strength, and time 

 in place before force application. The correlation was not sufficient for pre- 

 dicting breakout forces with an acceptable degree of accuracy in field 

 operations. 



In FY-70 (fiscal year 1970), an analysis of the previous partially 

 embedded object breakout test results was conducted under the sponsorship 

 of the Naval Facilities Engineering Command. This analysis led to the recom- 

 mendation that additional small-scale laboratory tests were needed to better 

 define the breakout problem. These were conducted in the NCEL Seafloor 

 Soils Laboratory during FY-71 and included approximately 90 tests performed 

 under carefully controlled conditions. The test results have been incorporated 

 into a general framework, discussed in later sections of this report. 



Test Work Done Outside NCEL. At least two organizations besides 

 NCEL have conducted unaided breakout tests involving objects partially 

 embedded in cohesive soil. The Southwest Research Institute conducted a 

 series of such tests within a 90-inch-diameter pressure vessel. The results were 

 considered preliminary and were not analyzed in detail. The authors concluded 

 that the breakout force is a function of object size, soil type, and in-situ time 

 and is not a function of the hydrostatic pressure.^ 



The Lockheed Missiles and Space Company performed a large number 

 of breakout tests in a reservoir near Santa Cruz, California, and in a test bin 

 filled with San Francisco Bay mud. The tests were begun by placing such 

 objects as 55-gallon oil drums and scale models of the Navy's DSRV (Deep 



