For the breakout problem, the situation can be diagrammed as 



-Cb 



pore water gage 

 pressure, p 



7^ 



>■ 



bottom of object 

 before load application 



where D = original embedment depth 



D' = portion of depth over which soil is in contact with object 

 side after load application 



B = object width 



Fgb = line force on object 



p = gage pressure in pore water beneath object (equal to total 

 pressure loss, Ap) = F^^/A 



F^J = force carried by soil = Fg[^ - W,^ + W^ 



Wjj = weight of object in water 



Wj = submerged weight of soil displaced by object 



A = cross-sectional area of object 



Water flows under the influence of pressure, p, into the zone in which 

 the soil is still in contact with the object side. The average flow rate, Q, can 

 be written as a volume of water per unit length, V^^, flowing over the time 

 required for breakout, t^^. 



Q = 



V. 



The volume of water per unit length which must flow before breakout 

 will occur is clearly proportional to the portion of embedment depth which is 

 in contact with the object side, D'. This volume is also proportional to some 



44 



