'^ It is important to note that for immediate breal<out the quantity 

 which must be predicted (the dependent variable) is the immediate breakout 

 force, whereas for long-term breakout the dependent variable is the breakout 

 time. 



The analysis of the breakout problem will begin with the subproblem 

 of predicting the immediate breakout force. 



Immediate Breakout 



The immediate breakout of partially embedded objects from cohesive 

 soils has many elements in common with the short-term bearing capacity of 

 small footings. In the case of breakout, if water is not permitted to flow into 

 the space created below the object as it moves upward (as it will not if the 

 terms of the definition of immediate breakout apply), then the soil itself 

 must flow into the space. The shearing pattern of the soil flowing into the 

 space will be similar to the shearing pattern of soil flowing away from an 

 object penetrating the ground during a bearing capacity failure. A discussion 

 of the technical aspects of this analogy is presented in Appendix B. In this 

 appendix, it is concluded that a rough first approximation of the immediate 

 breakout force may be obtained with a bearing capacity equation of the form 



^' = 5s(l.0 + 0.2|-Yl.0 + 0.2 |-) (1) 



where Fi,^ = portion of immediate breakout line force carried by soil — 

 hereafter referred to as the immediate breakout force 



= Fei, - w, + W3 



Fgit, = immediate breakout line force 



S = .representative undrained shear strength of soil (assumed 

 equal to S^, the vane shear strength) 



L = object length 



Other terms are as defined previously. (See page 8.) 

 For practically all of the NCEL tests, the objects were so shaped that 

 B was equal to L. 



For those objects. Equation 1 reduces to 



10 



