Soil Permeability | unitracc.de

Soil Permeability Coefficient: <div class="clearfix layout-row columns-2"><div class="layout-column first column-1"><div><p>The <strong>permeability coefficient k</strong> (also<br/>called k<sub>f</sub>) is used to measure the permeability of the soil.</p><p>Although some types of soil might appear visually the same, their k-values fluctuate considerably from site to site due to the <strong>framework of soil</strong>, the<strong> bedding density</strong> and the <strong>percentage of finest particles</strong> [Herth95]. Thus, these values can only be used for a rough estimation.</p></div></div><p>For civil engineering purposes, it is distinguished between the following permeability …</p></div>
Soil Permeability Coefficient (2): <div class="clearfix layout-row columns-2"><div class="layout-column first column-1"><p>Estimated values for the permeability of different types of soil.</p><p>(Table: Permeability coefficients k for various soil types)</p></div><div class="layout-column last column-2"><p>Permeability coefficient subject to the <strong>grading curves</strong>.</p><p>(Image: Permeability coefficient with reference of the particle size distribution curve [LWA89] [FI-Herreb])</p></div></div><p/>
How to Determine the Soil Permeability Coefficient? (1): <div class="clearfix layout-row columns-2"><div class="layout-column first column-1"><p>A precise method for determining the k-value for a certain groundwater area in situ involves lowering the groundwater using pumps [Herth95].</p><p>(Image: Groundwater lowering)</p></div><div class="layout-column last column-2"><p>In order to cover all traversed soil layers, the extraction well has to have the same depth as the wells of the future groundwater lowering system or pipe run.</p><p>As a general rule, the soil samples of the extraction well and all measuring level positions should be tested by means of …</p></div></div>
How to Determine the Soil Permeability Coefficient? (2): <p>Prior to the design and dimensioning of technical details, investigations according to [[ASTM D2434]] and/or [DIN18130-1:1998] should also be included. Their evaluation is based on the application of Darcy‘s law and, as a result, provides the permeability coefficient k.</p><div class="clearfix layout-row columns-4"><div class="layout-column first column-1"><div>(Formula: Permeability coefficient k according to Darcy‘s law)</div></div><div class="layout-column column-2"><div>(Image: Filter velocity v = Q (flow) / A (cross section))</div></div><div class="layout-column column-3"><div>(Image: Examples of permeability tests [Soos96] - Test arrangement …</div></div></div>
How to Determine the Soil Permeability Coefficient? (3): <p>(Image: Influence of the hydraulic gradient onto the permeability coefficient)</p><p>Darcy‘s law does not apply to coarse granular materials (turbulent flow).</p><p>In the test setting, the hydraulic gradient can be chosen according to practical aspects, as long as the flow behaviour is in line with Darcy‘s flow law (<strong>linear flow region</strong>), the particle structure is not changed and the flow of fluid does not cause a consolidation or swelling of the sample.</p><p>[Kolym98]</p>
Influence of the Hydraulic Gradient on the Soil Permeability Coefficient: <p>(Image: Influence of the average grain diameter d onto the limits of the linear region of the filter flow law)</p><p>In the cases where the flow behaviour is <strong>non-linear</strong>, the hydraulic gradient in the laboratory has to be adjusted to the field conditions. The limits of the linear flow region can be roughly estimated subject to the average particle diameter [DIN18130-1:1998].</p><p>Thus, for water permeability tests under prelinear or postlinear conditions in the …</p>
Calculation of Soil Permeability Coefficient Based on Particle Diameter: <p>In literature, you will find simple mathematical solutions for a practical, fast and approximate determination of the soil's water permeability, given a precise knowledge of the geological conditions. These solutions are especially useful for non-cohesive types of soil and they are dependent on the given particle size distribution. The most common formulas are listed below:</p><p>(Table: Calculation of soil permeability coefficient based on particle diameter)</p>
Beyer Nomogram for Determining the Soil Permeability Coefficient: <div class="clearfix layout-row columns-2"><div class="layout-column first column-1"><p>As the solution to his determined interrelations, Beyer provides an easy-to-handle nomogram, from which you can directly read off the water permeability for sands and gravels [Beyer64].</p><p>However, this method does not take sufficient account of decisive influencing factors (as e.g. the given bedding density). Thus, reliable data for the individual case of application can only be gathered by means of a test arrangement for the determination of the water …</p></div></div>