gsd - 53:030 Class Notes C.C Swan University of Iowa...

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Lecture 2: Grain Size Distributions and Soil Particle Characteristics A. Motivation: In soil mechanics, it is virtually always useful to quantify the size of the grains in a type of soil. Since a given soil will often be made up of grains of many different sizes, sizes are measured in terms of grain size distributions. Grain size distribution (GSD) information can be of value in providing initial rough estimates of a soil’s engineering properties such as perme- ability, strength, expansivity, etc. A subject of active research interest today is the accurate prediction of soil properties based largely on GSDs, void ratios, and soil particle characteristics. At this point in time, though, such research has not yet produced results that are usable in standard engineering practice. In this period, we will look at methods of measuring GSDs of soils, and also different measures of soil grain shapes. When measuring GSDs for soils, two methods are generally used: -> For grains larger than 0.075mm sieving is used; -> For grains in the range of .075mm > D > 0.5 μ m, the hydrometer test is used. 1 53:030 Class Notes; C.C. Swan, University of Iowa
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B. Sieve Testing (for coarse-grained soils with D > 75 μ m) 2 3" 1.5" 0.75" 0.375" #4 #6 #8 #10 #16 #20 #30 #40 #50 #60 #80 #100 #140 #170 #200 #270 pan i=1 i=2 i=3 . . . i=n Passes soil of diameter less than: 3" 1.5" 0.75" 0.375" 4.750mm 3.350mm 2.360mm 2.000mm 1.180mm 0.850mm 0.600mm 0.425mm 0.300mm 0.250mm 0.180mm 0.150mm 0.106mm 0.088mm 0.075mm 0.053mm 0.000mm Gravels Sands 53:030 Class Notes; C.C. Swan, University of Iowa
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Procedure for Sieve Testing of Soils: a) Pour oven-dried soil of mass M
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gsd - 53:030 Class Notes C.C Swan University of Iowa...

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