Application of a safety factor of 2 yields a design breakout time 

 of 22 hours. This might be a reasonable time to wait for breakout 

 to occur. If not, breakout aids should be applied. 



SUMMARY AND CONCLUSIONS 



1 . Breakout of partially embedded objects from cohesive seat loor soils can 

 be divided into immediate and long-term breakout. Immediate breakout 

 involves rapidly increasing the upward force on an embedded object until 



it becomes detached. Long-term breakout involves applying a force less than 

 the immediate breakout force and allowing time to pass. If embedment is 

 partial (embedment depth less than object width) breakout will eventually 

 occur under the influence of almost any net uplift force. However, much 

 time may be involved. 



2. The immediate breakout force problem appears similar to the problem of 

 determining the bearing capacity of shallow footings. However, the basic equa- 

 tions must be modified somewhat to reflect differences between failure 

 mechanisms. 



3. The techniques of this report are capable of predicting the immediate 

 breakout force (that is, that portion in addition to the object weight) within 

 plus or minus 50%. This is a suitable accuracy for a seafloor object retrieval 

 operation. 



4. The breakout forces required for objects very shallowly embedded 

 (embedment depth less than one-tenth the object width) are almost negli- 

 gible. 



5. No existing theoretical techniques appear applicable to the long-term 

 breakout problem. However, the empirical approach presented in this report 

 provides a means for predicting the breakout time within about plus or minus 

 100%. This is a reasonable accuracy for a time-dependent soil mechanics pro- 

 blem and appears adequate for the types of operations toward which this 

 approach will be applied. 



RECOMMENDATIONS 



1 . The procedures presented in this report should be used to predict the 

 immediate breakout force and the time required for breakout when a force 

 less than the immediate breakout force is applied. 



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