TABLE 6-1 

 Comparison of Sieve Grades 



Wentworth Classification 



Boulder, over 256 mm 

 Cobble, 64 to 256 mm 

 Pebble, 4 to 64 mm 



Preparation of Sample 



The size of sample to be used is discussed in Catalogue No. 53, published 

 by W. S. Tyler Company (Cleveland, Ohio). 



The general rule in determining the size of a sample is that it be 

 limited in weight so that no sieve in the series used in the analysis 

 be overloaded. Overloading is most likely to occur in making analyses 

 on closely graded materials where the range of particle size is confined 

 to close limits. In this case the size of sample should be determined by 

 the capacity without overloading of the sieve retaining the largest 

 amount of sample. Overloading of the sieves results in unreliable data 

 as blinding of the meshes occurs on the heavily loaded sieve. 



The Tyler catalogue recommends 25 to 100 grams for closely graded 

 materials. Krumbein and Pettijohn (1938) suggest 25 grams, whereas Twen- 

 hofel and Tyler ( 1941 ) prefer 40 grams. A review of current literature indicates 

 that many workers use 50 to 100 grams. The screen diameter must be considered 

 in selecting the weight of sample to be used. It is assumed that, where sample 



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