Holding Capacity 



Soil categories A and C (cohesive soils) were analyzed for both 

 long term and short term behavior under static loading. Soil category D 

 (cohesionless) was analyzed for long term static loadings. Anchors con- 

 sidered were flat plates with areas from 9.3 nr to 149 m (100 -ft to 

 1600 ft 2 ). Calculations were made for both square and rectangular (length 

 = 2 x width) plates. Holding capacities at anchor embedment depths of 

 6.1 m to 30.5 m (20 ft to 100 ft) were determined. The procedure proposed 

 by Taylor and Lee (1972) was used. 



Short Term Holding Capacity . Short term static loading describes 

 the situation in which the anchor is loaded rapidly until breakout occurs. 

 For short term loadings the holding capacity to be achieved is calculated 

 differently for cohesive soils (clays) than for cohesionless soils (sands). 



In cohesive soils the excess soil pore pressure generated by rapid 

 loading acquires a lengthy time period for near-complete dissipation. 

 Because the pore pressure beneath an embedment anchor plate does not have 

 sufficient time to dissipate during rapid loading, suction develops under 

 the plate causing an apparent increase in holding capacity. The magni- 

 tude of this suction force cannot be predicted confidently for the highly 

 disturbed soil expected about the large 0TEC plate anchors. ' Because of 

 this lack of confidence, the contribution of the suction force to short- 

 term holding capacity was herein conservatively assumed to be zero; i.e. 

 no suction. 



In cohesionless soils the excess soil pore pressure due to rapid 

 loading is dissipated almost as fast as it is generated. Thus, a suction 

 force is not generated. 



The basic equation used for holding capacity is a typical bearing 

 capacity equation (Taylor et al . , 1975): 



R = A(sN c + ydN q )(0.84 + 0.16 B/Z) ( 2 ) 



where R = holding capacity (N) 



A = plate area (m ) 



s = soil cohesion (Pa) 



y = buoyant unit weight of soil (N/m ) 



d = plate embedment (m) 



N c , Nq = holding capacity factors 



B = fluke width (m) 



Z = fluke length (m) 



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