Information on the breakout forces necessary to extract objects 

 that are embedded in the seafloor is not plentiful; however, there is 

 considerable information on this subject regarding terrestrial soils. 

 Unfortunately, most of this information is related to the breakout 

 resistance of shallow ly embedded objects. Common practice has been 

 to extend shallow breakout theory to the case of deeply embedded objects. 

 This procedure is not applicable to extending shallow foundation design 

 theory to deep foundation theory so it is probable that this procedure 

 is not applicable to the similar problem of anchor breakout. Therefore, 

 new analytical techniques were required to determine the breakout 

 resistance of deeply embedded objects. 



Results of the research on shallow anchors indicate that such 

 anchors form failure surfaces that are dependent upon soil type and 

 soil density. Small-scale model tests at Duke University (Equivel-Diaz, 

 1967; Ali, 1968; and Bhatnagar, 1969) show that the shape shown in 

 Figure 2 4 occurs only in the case of relatively shallow anchors in 

 dense sand or stiff clay. For shallow anchors in loose sand or soft 

 clay, the slip surface, though not clearly established, is closer to 

 being a vertical cylinder around the perimeter of the anchor. 



Figure 24. Slip surface for a shallowly embedded 

 circular plate. 



Deeply embedded anchors do not fail the soil in general shear 

 failure such as that shown in Figure 24, regardless of the relative 

 density of the soil. Experiments indicate that they can be moved 

 vertically for considerable distances by producing a failure pattern, 

 Figure 25, similar to punching shear failures in deep foundations 

 (Vesic, (1969). Only after being pulled up to relatively shallow depths 

 may they eventually produce general shear failures such as shown 

 in Figure 24. 



47 



