Grain Size Distribution

Why Is Grain Size Distribution Important?: <p>The primary distinctive feature of mineral soil is the <strong>grain size</strong> of the individual particles. The determination of the grain size is the first step in the designation- and classification process of a certain type of soil. </p><p>(Image: Soil grain sizes from 0 – 4 mm) (Image: Soil grain sizes from 4 – 25 mm)</p>
Soil Particle Size Scales for Soil Classification Purposes: <p>An important factor in soil classification presented in the upcoming pages is the soil particle size (grain size). Two scales are used for classification purposes of soil grain size: the US Sieve Series and the Tyler Equivalent. The table below presents the most common sieve mesh opening sizes for these two scales is presented in the table below.</p><p>(Table: US sieve mesh size)</p>
Grain Size Distribution: <table><tbody><tr><td> <p>The <strong>grain size distribution</strong> “determines the mass percentages of the various grain size ranges found in a soil sample”.</p><p>The particle size distribution is illustrated using the <strong>grading curve</strong> (grain size distribution curve) and determined by dry screening. The grading curve y(d) defines the mass percentage y of the particles with a diameter smaller than d in a given sample [[ASTM D422]] [DIN18123].</p></td> <td> (Image: Laboratory sieve shaker used to determine …</td></tr></tbody></table>
Grain Size Distribution Using Sieve Analysis and Hydrometer Method: <table><tbody><tr><td> <p>If the mass percentage of the grains with a diameter smaller than 0.0025 in (0.063 mm) in a given soil sample is small (≤ 3%), the grain size distribution curve can be determined by dry screening only.</p><p>If the mass percentages of these small grains are too high, a combined screening- and <strong>sedimentation analysis or hydrometer method</strong> has to be carried out.</p><p>“In the sedimentation process the grain size distribution of the particle percentages that are smaller …</p></td></tr></tbody></table>
Grain Size Curve: <p>The cumulative frequency polygon of the mass percentages of the given soil sample is called <strong>a grading curve (or grain size curve),</strong> and is used for a definite designation of the soil.</p><div>(Image: Grading curves of some characteristic types of soil [Neuma64])</div>
Graphical Classification of Grain Sizes: <p>(Image: Grain sizes classification)</p><p>(Table: Soil characteristics)</p>
Example of Determining the Grain Size Distribution of a Soil Sample: <div class="clearfix layout-row columns-2"><div class="layout-column first column-1"><p><strong>Example:</strong> The measured values of the sedimentation analysis resulted in the following mass percentages:</p><p>(Formula: Aus den Messwerten der Siebanalyse folgten die Gewichtsanteile)</p><p>With ∑m (D < d) as the percent passing (percentage by weight) through the screen with the mesh size d and ∑ m(D) as the total mass of the sample. Consequently: (Formula: Gewichtsanteil y(0,063))</p><p>(Formula: Gewichtsanteil y(0,125))</p><p>(Formula: Gewichtsanteil y(0,25))</p></div><div class="layout-column last column-2"><div><strong>Table</strong>: Dry screening …</div></div></div>
Grain Size Distribution of Non-Cohesive Soils: <table><tbody><tr><td> <p>The following particle size distinctions are made when grading non-cohesive types of soil:</p><p><strong>Well-graded particle size distribution: </strong>The continuous grading curve traverses several particle size ranges. All particle sizes involved are partially present (see Image, e. g. curves 3 and 4).</p><p><strong>Poorly-graded particle size distribution (uniformly graded):</strong> The grading curve runs steeply and, in the extreme case, it remains in just one particle size range (see …</p></td></tr></tbody></table>