1 . When a net upward force is applied to an embedded object, and 

 the object does not breal< out immediately, the force must be balanced by 

 the development of tensile stresses in the underlying soil. Although most soils 

 are incapable of existing in a state of tension indefinitely, most cohesive soils 

 are capable of resisting tension for moderate to long periods of time, depend- 

 ing upon the soil permeability and the overall drainage conditions. Breakout, 

 therefore, is a distinctly time-dependent process; practically any net upward 

 force will dislodge a partially embedded object if enough time is allowed to 

 pass. 



2. Breakout is strongly influenced by slight variations and inhomo- 

 geneities. For example, a single seam of sand connecting the bottom of a 

 partially embedded object with a source of free water could almost completely 

 eliminate the resistance of the soil to net upward forces on the object. Another 

 object in exactly the same situation without the sand seam might require a very 

 large breakout force or a long breakout time. 



Breakout, therefore, is a complex time-dependent problem not unlike 

 the problem of predicting the time— settlement history of foundations. This 

 latter problem has been researched extensively, and it is still difficult to make 

 an accurate prediction. Considering that breakout is even more strongly influ- 

 enced by slight variations in soil properties and that considerably less research 

 has been directed towards understanding it, it is doubtful that a truly accurate 

 technique for predicting breakout force— breakout time characteristics can be 

 developed. With the amount of test data presently in existence, however, it 

 is possible to derive somewhat approximate techniques for making first-order 

 estimates. 



In developing these approximate techniques, it is first necessary to 

 clearly separate the breakout problem into two subproblems: immediate 

 breakout and long-term breakout. 



I mmediate breakout is defined in soil mechanics terms as breakout 

 under short-term, undrained loading conditions. Loading is so rapid that no 

 significant amount of water is allowed to flow into or through the underlying 

 soil. In practical terms, immediate breakout occurs when the upward load on 

 the embedded object is increased as rapidly as the available equipment will 

 permit until the object breaks free of the seafloor. 



Long-term breakout is defined as breakout occurring under the 

 influence of a force less than the immediate breakout force. A certain amount 

 of time must pass before this smaller force will accomplish what the larger force 

 accomplished in very little time. Long-term breakout is of interest because 

 immediate breakout often requires a large amount of equipment to achieve. 

 It may often be more economical to apply a small force and wait for a period 

 of time (perhaps several hours or even a few days). In soil mechanics terms, 

 long-term breakout corresponds to partially drained or shear creep loading. 



