should be reduced to either uniform or linearly increasing strength 

 whenever possible. 



The same sort of characteristic property selection technique would 

 probably also be valid for sand. However, since the determination of 

 the variation of sand properties is difficult, this procedure is not 

 recommended. Rather, the standard properties listed previously should 

 be used. 



SUGGESTED PREDICTION PROCEDURE 



In order to simplify the holding capacity prediction process, the 

 suggested procedures which were discussed previously are listed in this 

 section without rationale. This general procedural framework is shown 

 by the block diagram of Figure 8 with each item of the diagram being 

 discussed briefly below. The numbering system below compares with that 

 of the diagram. 



In virtually all cases, an anchor should be installed so as to 

 display "deep" behavior. In all of the curves of holding capacity or 

 holding capacity parameters versus depth, there are breaks below which 

 the holding capacity increases less rapidly. This behavior in the 

 lower sections of these plots is termed "deep", and it is advantageous 

 to establish a "deep" anchor because errors in locating the anchor, 

 either during installation or because of deformations after installation, 

 do not cause large changes in holding capacity. The anchor is, therefore, 

 more reliable. 



Hansen (1953) has shown that holding capacity may increase up to 

 25 percent in clay if plates are rough rather than smooth. Therefore, 

 to improve holding capacity plates could be ritted, grouved, or simply 

 allowed to rust. 



A step by step approach for calculating anchor holding capacity 

 is as follows : 



1. Determine Design Parameters . Determine the anchor fluke embed- 

 ment depth, D, width, B, length, L, and area, A. In a typical design 

 problem, the anchor dimensions would be trial values. The engineer 

 would proceed through the calculations to obtain an estimated holding 

 capacity and then determine if it satisfies the design criteria for 

 the anchored system. If not, an iterative procedure would follow with 

 different anchor system parameters being tried until a satisfactory 

 solution was developed. 



Estimating the embedment depth, D, may become a major problem in 

 itself depending upon the means used for anchor installation. Typical 

 pile driving equations may be used approximately for vibratory and 

 impact installation; and the techniques of NCEL (1971) may be applied 

 to free fall and, very approximately, to explosive embedment. Research 

 currently underway at NCEL will provide improved techniques for pre- 

 dicting penetration behavior. 



12 



