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Effective Grain Sizes

<div class="clearfix layout-row columns-2"><div class="layout-column first column-1"><p>The grading curve results in essential <strong>curve parameters</strong> that require a prior determination of d₁₀, d₃₀ and d₆₀.</p><table><tbody><tr><td> <p>d₁₀ =</p></td> <td> <p>Particle size, of which 10 % by weight are finer than d.</p></td> </tr><tr><td> <p>d₃₀ =</p></td> <td> <p>Particle size, of which 30 % by weight are finer than d.</p></td> </tr><tr><td> <p>d₆₀ =</p></td> <td> <p>Particle size, of which 60 % by weight are finer than d.</p></td> </tr></tbody></table><p>By means of these details the curve parameters C_U(coefficient of uniformity)&#160;and C_C&#160;(coefficient of curvature) can be calculated to describe the &#8230;</p></div></div>

Curve Parameters

<div class="clearfix layout-row columns-2"><div class="layout-column first column-1"><p>The shape parameters of the grain size distribution curve are determined by the <strong>coefficient of uniformity C_U</strong>&#160;(in [DINENISO14688:2001]&#160;and [[ASTM D6913]]&#160;) and the coefficient of curvature C_C.</p><p>(Formula: Calculation of the coefficient of uniformity CU)</p></div><div class="layout-column last column-2"><p>The coefficient of uniformity&#160;C<span>U</span>&#160;specifies the average inclination (slope) of the grading curve that has been determined according to [[ASTM D422]] and/or&#160;[DIN18123], whereas the <strong>coefficient of curvature &#8230;</strong></p></div></div>

Coarse Soil Classification Based on Curve Parameters

<p>A well-graded grain size distribution is present, if C<span>U</span>&#160;&#8805; 6 and 1 &#8804; C<span>C</span>&#160;&#8804; 3, whereas a poorly-graded or intermittent grain size distribution holds true for all other cases (table). However, according to&#160;[Estermann (1994)], these determinations are to be slightly limited, as both criteria can also hold true for certain discontinuously running grading curves.</p><p>(Table: Classification of coarse types of soil depending on the coefficient of uniformity and &#8230;</p>

Very Coarse Soil Classification

<p>The classification of very coarse types of soil according to the table requires very large samples. In that case, it is impossible to extract representative samples from borings [DINENISO14688:2001].</p><p>(Table: Classification of very coarse soil as per ISO 14688-2)</p>

Why Is It Important to Know the Coefficient of Uniformity?

<div class="clearfix layout-row marginalia"><div class="layout-column side-note"><div>(Image: Attention!)</div></div><div class="layout-column text"><p>Using the grading curves and the <strong>coefficient of uniformity C<span>U</span></strong>, a first essential conclusion can be derived on the compactness- or displacement capability, as well as water permeability of the soil.</p></div></div><p/><p/>

Why Is It Useful to Know the Grain Size Distribution of the Soil?

<p>In any case of specific application, the existing site-specific grain size distribution of the soil should always be determined, using the already known results from other sites in the vicinity could have distortive effects. This is illustrated by the following grain distribution curves of various soil samples collected in the German city of Hamburg. They clearly illustrate the variety of grain sizes and soil uniformity of soil samples collected &#8230;</p>