ballpoint ink on plastic strip (plastic orange flagging commonly used by- 

 surveyors). Some information may be preprinted by rubber stamp on the 

 plastic strip using indelible laundry ink. The advantage is that the 

 label can be stored in the bag with the wet sample without the label 

 deteriorating or the information washing or wearing off. 



4.27 SIZE ANALYSES 



Three common methods of analyzing a beach sediment for size are: 

 visual comparison with a standard, sieve analysis, and settling tube 

 analysis. 



The mean size of a sand sample can be estimated qualitatively by 

 visually comparing the sample with sands of known sizes. Standards can 

 be easily prepared by sieving out selected diameters, or by selecting 

 samples whose sizes are already known. The standards may be kept in 

 labeled treinsparent vials, or glued on cards. If glued, care is neces- 

 sary to ensure that the particles retained by the glue are truly repre- 

 sentative of the standard. 



Good, qualitative, visual estimates of mean size are possible with 

 little previous experience. With experience, such visual estimates 

 become semiquantitative. Visual comparison with a standard is a useful 

 tool in reconnaisance, and in obtaining interim results pending a more 

 complete laboratory size analysis. 



4.271 Sieve Analysis . Sieves are graduated in size of opening according 

 to the U.S. Standard series. These standard sieve openings vary by a fac- 

 tor of 1.19 from one opening to the next larger (by the fourth root of 2, 

 or quarter phi intervals), e.g., 0.25, 0.30, 0.35, 0.42, and 0.50 milli- 

 meters (2.00, 1.75, 1.50, 1.25, 1.00 phi). The range of sieve sizes used, 

 and the size interval between sieves selected can be varied as required. 

 Typical beach sand can be analyzed adequately using sieves with openings 

 ranging from 0.062 to 2.0 millimeters (4.0 to -1.0 phi), in size incre- 

 ments increasing by a factor of 1.41 (half-phi intervals). 



Sediment is usually sieved dry. However, for field analysis or for 

 size analysis of sediment with a high content of fine material, it may be 

 useful to wet-sieve the sediment. Such wet-sieve analyses are described 

 by (e.g., Lee, Yancy, and Wilde, 1970, p. 4). 



Size analysis by sieves is relatively slow, but provides a widely 

 accepted standard of reference. 



4.272 Settling Tube . Spherical sedimentary particles settle through 

 water at a speed that increases as the particle weight increases. Since 

 most sand is approximately spherical quartz, or calcium carbonate with a 

 specific gravity near quartz, particle size is proportional to particle 

 weight. Thus fall velocity can be used to measure size, (e.g., Colby and 

 Christensen, 1956; Zeigler and Gill, 1959; and Gibbs, 1972.) Figure 4-31 

 shows fall velocity for quartz spheres as a function of temperature. 



4-26 



