F. (cohesive soil) 



A(c'N^ + Y^ D N )(0.84 + 0.16 B/L) 



A, Y, 



1 'b' 



It 



BjL 



N' 



c 



Long-term holding 

 capacity 



Soil cohesion 

 intercept 



Refer to short-term 

 section 



Holding capacity 

 factor drained/ 

 frictional condition 

 (Refer to short-term 

 section) 



Long-term holding 

 capacity factor for 

 cohesive soil 



Loose/soft seafloors - failure associated with relatively 

 large displacements; reduce c' , <|) by 1/3. c = 2/3c* , 

 ^ = tan~-'-(tan 2/3 ({>) 



Creep rupture - cohesive soi l - increasing rate of shear until 

 failure occurs (poorly understood phenomenon) 



- Problem appears minimal for calcareous ooze, pelagic clay. 



- F X S = 2 adequate to prevent creep rupture. 



c. Dynamic Holding Capacity 



1) Impulse Loading - refer to Douglas (1978), or Beard 

 (1980), for details of prediction procedure. 



- Consider only if large infrequent loads may be 

 unexpectedly applied to a plate anchor mooring. 



- Can have a positive effect on anchor holding capa- 

 city for loads of up to: 



• 500 sec duration - cohesive soil 



• 10 sec duration . - cohesionless soil 



- For load durations < .01 sec impulse holding 

 capacity can be: 



2-5 times short-term capacity for a normally 

 consolidated clay. 



2-6 times short-term capacity for a mid-density 

 sand 



- Impulse loads near or somewhat above F can be 

 tolerated. 



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