4. FLUKE KEYING 



Fluke keying is the process of turning the fluke from the edge-on 

 orientation of penetration to an orientation that presents a large area to 

 resist pullout. During keying, fluke embedment depth is reduced. 

 Therefore, holding capacity is calculated at this reduced depth, the 

 embedment depth of the fluke. The embedment depth is arrived at by 

 subtracting the fluke keying distance from the penetration depth. 



It is generally thought that the breakout load must be applied to 

 achieve full keying. However, it is not necessary to fully key the 

 anchor/fluke for it to perform properly. In-service loads that exceed 

 the keying load applied at installation will achieve additional keying. 



In cohesive soils there may be an influence of time on keying 

 distance. Rocker (1977) showed that in a clay with a sensitivity of 2 

 to 3, waiting about 1 hour after embedment improved the keying dis- 

 tance to two fluke lengths compared to three to four fluke lengths after 

 waiting only 1/4 hour. Since Rocker's study, improvements have been 

 made in the fluke design to shorten keying distance. With the 

 improved flukes, CEL field tests in a soft clay of similar sensitivity 

 showed the flukes keyed in two fluke lengths or less with less than 1/4 

 hour wait after embedment (Clausner, 1978). In view of this recent 

 data, fluke keying distance in cohesive soils can be taken as two fluke 

 lengths . 



For cohesive soil, the embedment depth is estimated from: 



D = D - 2 L (4-1) 



P 



For cohesionless soils, the embedment depth is estimated from: 



D = D - 1.5 L (4-2) 



P 



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