This relationship summarizes the extent to which previous soil 

 mechanics research can be applied to the problem of breakout. To refine 

 the process of predicting immediate breakout forces still further, it is neces- 

 sary to resort to empirical breakout data. This was done by first selecting a 

 criterion for separating immediate breakout tests from long-term breakout 

 tests. For the field tests and the FY-69 laboratory tests, a breakout time of 

 10 minutes was set as the division between the two because this time was 

 required for load application. For the FY-71 tests, immediate and long-term 

 tests were conducted differently. The immediate breakout tests were per- 

 formed by increasing the line load until breakout occurred; whereas the 

 long-term breakout tests were performed by applying a line force equal 

 to some fraction of the estimated immediate force. 



The data from the immediate breakout laboratory tests were correlated 

 by plotting the experimentally determined term, Fji^/AS, versus D/B, a tech- 

 nique suggested by the form of Equation 2. This plot is given by Figure 1 . 

 1 1 1 1 1 



Equation2__ 



.- Tii^^anTcs relations! 



-<3> (existing 5°'""^ 



i 

 t 



;hip^ 



-• • 



k* 



• FY-71 laboratory tests 

 O FY-68 laboratory tests 



Sy = vane shear strength 

 J I 



0.4 0.6 



Normalized Embedment Depth 



0.8 

 D 



Figure 1. Normalized immediate breakout force versus normalized embedment 

 depth — laboratory tests. 



15 



