moment of the pile section is reached. The short-rigid pile case will nor- 

 mally suffice for anchor piles for floating breakwaters. The short-rigid pile 

 is assumed not to bend when laterally loaded but will rotate about a point 

 approximately one-third to one-quarter its length above the pile tip. Anchor 

 piles are designed for the soil's ultimate lateral resistance rather than 

 deflection of the pile head; hence, the design is predicated on sufficiently 

 large deflection to develop the full passive resistance. This is defined as 

 three times the Rankine passive earth pressure from the soil surface to the 

 center of rotation. The expression for the ultimate lateral resistance of a 

 short pile in a cohesionless soil is 



(Y S D* 3 K ) 



F.F = — (5) 



c s (2e + 2£) 



and 



(1 + sin d>) 



Kn = ~ (6) 



(1 - sin <J>) 



P 



where 



D = pile diameter 



y = unit weight of soil 



K = Rankine' s coefficient of passive earth pressure 



e = distance load is applied above the bottom 



£ = distance pile penetrates into the bottom 



<j> = internal friction of sand 



Equation (5) may be solved by iteration unless the dimension e is zero. In 



that case, the lever arm of the load vanishes and the load is applied directly 



at the firm bottom. Equation (5) can then be solved directly for the required 

 pile distance as 



< 2F t F s> 

 (Y s DK p )J 



(7) 



When the foundation soil conditions at the breakwater site are cohesive, 

 Broms' (1964) method can be used to determine the ultimate lateral resistance 

 of a rigid-pile anchor under lateral load. The distance the pile penetrates 

 into the bottom is 



I = 1.5D + f + q (8) 



where 



(F F ) 

 t s 

 f = (9) 



(9c D) 



and 



[F F (e + 1.5D + 0.5f)°* 5 ] 

 q =_ U (10) 



(2.25D) 



30 



