if static terms are most significant the development of such a scheme 

 could be relatively simple. Also, a survey penetrator would be of 

 less value if the measured data included a complex combination of 

 static and viscous quantities. More controlled research of the nature 

 of that reported herein is required to determine more precisely what 

 are the important factors affecting penetration. 



SUGGESTED PREDICTION TECHNIQUE 



Although there are presently many unanswered questions concerning 

 the nature of the penetration mechanism, in practical situations it may 

 be necessary to predict penetration responses before additional research 

 can be performed. Therefore, one approach must be selected for use 

 during this interim period. On the basis of the research and analyses 

 presented above, it appears that the most accurate procedure currently 

 available is a "pseudo-static" approach using remolded strengths. 

 The slight additional accuracy brought about by the use of velocity- 

 dependent soil resistance terms does not appear to be justifiable 

 at present. 



A procedure for using this approach in predicting penetration 

 depth given entry velocity, soil strength profile, and object geometry, 

 is presented below. The procedure could be inverted to yield soil 

 strength characteristics given a penetration response. 



1. The surface area of the object should be resolved into 

 horizontal and vertical components. Progressing up the object from 



the bottom, the total horizontal and vertical surface area corresponding 



to each finite increment of object length should be calculated. A 



typical length increment, A£, for a moderate size object would be 



perhaps six inches. For each increment the horizontal area should 



be multiplied by 10.0 and added to the vertical area. This is to 



account for the increased soil resistance encountered by horizontal 



surfaces. This sum is identified as the effective area coefficient A . 



e 



2. The effective area coefficient, A , should be tabulated as 

 a function of the vertical distance from the bottom of the object. 



3. An estimate of the remolded strength, c , versus sediment 



s 

 depth, ^ , should be made for the site. This may be obtained from 



laboratory tests on core samples, in situ tests, or through 



consultation with a soil engineer acquainted with the general area. 



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