{"id":3505,"date":"2024-09-04T17:49:02","date_gmt":"2024-09-04T12:19:02","guid":{"rendered":"https:\/\/study.madeeasy.in\/?p=3505"},"modified":"2025-08-13T12:03:33","modified_gmt":"2025-08-13T06:33:33","slug":"permeability-of-soil","status":"publish","type":"post","link":"https:\/\/www.madeeasy.in\/study\/ce\/soil-mechanics-foundation-engineering\/permeability-of-soil","title":{"rendered":"Permeability of Soil"},"content":{"rendered":"<p style=\"text-align: justify;\">Soil is a particulate material and has pores that provides a passage for water. Such passages vary in size and are interconnected. The permeability of soil is a property which describes quantitatively, the ease with which water flows through that soil.<\/p>\n<h2 style=\"text-align: justify;\">Darcy\u2019s Law<\/h2>\n<p style=\"text-align: justify;\">The flow of free water through soil is governed by Darcy\u2019s Law. Darcy established that the flow occurring per unit time is directly proportional to the head causing flow and the area of cross-section of the soil sample but is inversely proportional to the length of the sample, i.e.<\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-3506 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/darcy-law.jpg\" alt=\"Darcy\u2019s Law\" width=\"421\" height=\"204\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/09\/darcy-law.jpg 421w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/09\/darcy-law-300x145.jpg 300w\" sizes=\"auto, (max-width: 421px) 100vw, 421px\" \/><\/p>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_79_1 ez-toc-wrap-left counter-hierarchy ez-toc-counter ez-toc-light-blue ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.madeeasy.in\/study\/ce\/soil-mechanics-foundation-engineering\/permeability-of-soil\/#FACTORS-AFFECTING-PERMEABILITY\" >FACTORS AFFECTING PERMEABILITY<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.madeeasy.in\/study\/ce\/soil-mechanics-foundation-engineering\/permeability-of-soil\/#PERMEABILITY-OF-STRATIFIED-SOILS\" >PERMEABILITY OF STRATIFIED SOILS<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.madeeasy.in\/study\/ce\/soil-mechanics-foundation-engineering\/permeability-of-soil\/#Horizontal-Flow\" >Horizontal Flow<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.madeeasy.in\/study\/ce\/soil-mechanics-foundation-engineering\/permeability-of-soil\/#Vertical-Flow\" >Vertical Flow<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"FACTORS-AFFECTING-PERMEABILITY\"><\/span>FACTORS AFFECTING PERMEABILITY<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">The permeability depends on the soil properties and fluid properties both.<br \/>\nThe Kozney-Carman equation is quite useful, it reflects the effect of factors that affect permeability.<\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-3507 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/kozney-carman.jpg\" alt=\" Kozney-Carman\" width=\"151\" height=\"47\" \/><\/p>\n<p style=\"text-align: justify;\"><strong>(a) Grain Size:<\/strong><\/p>\n<p style=\"text-align: justify;\">The coefficient of permeability (k) includes D<sup>2<\/sup><sub>10<\/sub> , where D<sub>10<\/sub> is a measure of grain size.<\/p>\n<p style=\"text-align: justify;\">i.e. k \u03b1 D<sup>2<\/sup><sub>10<\/sub><\/p>\n<p style=\"text-align: justify;\">If the void ratio is same, then permeability is more in coarse soil than in fine soil.<\/p>\n<p style=\"text-align: justify;\">l<sub>gravel<\/sub> &gt; k<sub>sand<\/sub> &gt; k<sub>silt<\/sub> &gt; k<sub>clay<\/sub><\/p>\n<p style=\"text-align: justify;\"><strong>(b) Void ratio:\u00a0<\/strong><\/p>\n<p style=\"text-align: justify;\">\u2022 As per Kozeny-Carman equation, coefficient of permeability is directly proportional to e<sup>3<\/sup> \/ 1+e<\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-3508 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/void-ratio.jpg\" alt=\"Void Ratio\" width=\"263\" height=\"48\" \/><\/p>\n<p style=\"text-align: justify;\">\u2022 If particle size is same, then loose soils are more permeable than dense soils.<br \/>\n\u2022 The plot of void ratio (e) against permeability k (at log scale) is approximately a straight line for all soils.<\/p>\n<p style=\"text-align: justify;\"><strong>(c) Particle shape:\u00a0<\/strong><\/p>\n<p style=\"text-align: justify;\">\u2022 It is expressed in terms of specific surface area and permeability relates to specific surface area.<\/p>\n<p style=\"text-align: justify;\">k \u03b1 1 \/ S<sup>2<\/sup><\/p>\n<p style=\"text-align: justify;\">\u2022 The angular particles have greater specific surface than the rounded particles.<br \/>\n\u2022 For the same void ratio, the soils with angular particles are less permeable than those with rounded particles.<\/p>\n<p style=\"text-align: justify;\"><strong>(d) Degree of Saturation:<\/strong><\/p>\n<p style=\"text-align: justify;\">Permeability is directly proportional to degree of saturation i.e k \u03b1 Degree of saturation (S).<br \/>\nIn partially saturated soils, entrapped air causes blockage in the flow of water. Hence, the permeability of partially saturated soil is lesser than that of a fully saturated soil.<\/p>\n<p style=\"text-align: justify;\"><strong>(e) Entrapped air and gases:<\/strong><\/p>\n<p style=\"text-align: justify;\">Entrapped air and gases in the voids obstruct flow and cause the reduction of permeability.<br \/>\nAs far as possible, sample should be fully saturated before the permeability test.<\/p>\n<p style=\"text-align: justify;\"><strong>(f) Structure of Soil particles:<\/strong><\/p>\n<p style=\"text-align: justify;\">For stratified soils, permeability is more in horizontal direction as compared to the vertical direction.<\/p>\n<p style=\"text-align: justify;\"><strong>(g) Properties of pore fluid:<\/strong><\/p>\n<p style=\"text-align: justify;\">The coefficient of permeability also includes \u03b3w\/\u00b5<\/p>\n<p style=\"text-align: justify;\">i.e. k \u03b1 \u03b3w\/\u00b5<\/p>\n<p style=\"text-align: justify;\">For water, relatively the unit weight remain constant but viscosity (\u00b5) decreases with increasing temperature.<\/p>\n<p style=\"text-align: justify;\">i.e. \u00b5 \u03b1 1 \/ T<\/p>\n<p style=\"text-align: justify;\">Hence, k \u03b1 T<\/p>\n<p style=\"text-align: justify;\"><strong>(h) Adsorbed water:<\/strong><\/p>\n<p style=\"text-align: justify;\">Adsorbed water or water film which is strongly attached to the soil solids, reduces flow area available for passage of water, which reduces permeability to some extent.<\/p>\n<p style=\"text-align: justify;\"><strong>(i) Impurities:<\/strong><\/p>\n<p style=\"text-align: justify;\">Due to presence of impurities, voids are blocked and the permeability is reduced.<\/p>\n<p style=\"text-align: justify;\"><strong>(j) Presence of minerals in water:<\/strong><\/p>\n<p style=\"text-align: justify;\">\u2022 The permeability of clay, depends upon the cation absorb on the surface of mineral.<br \/>\n\u2022 If void ratio is constant, the permeability is increased in the following order.<\/p>\n<p style=\"text-align: justify;\">k &lt; Na &lt; H &lt; Ca for montmorillonite<\/p>\n<p style=\"text-align: justify;\">Na &lt; k &lt; Ca &lt; H for K<\/p>\n<p style=\"text-align: justify;\">\u2022 For the construction of core of earthen dams, the clay being treated with salt water (Na-water) so that seepage can reduced.<\/p>\n<p style=\"text-align: justify;\"><strong>(k) Effect of effectiveness:<\/strong><\/p>\n<p style=\"text-align: justify;\">As effective stress increases, void ratio decrease and consequently permeability decreases.<\/p>\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"PERMEABILITY-OF-STRATIFIED-SOILS\"><\/span>PERMEABILITY OF STRATIFIED SOILS<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">In nature, soils are usually deposited in successive layers. Even if the different layers of the deposit are homogeneous within themselves, this may lead to a considerable disparity in the average permeability parallel to the bedding plane and that normal to the bedding planes.<br \/>\nBroadly, stratification can be considered as horizontal and continuous, average coefficient for flow in horizontal and vertical directions can be estimated.<\/p>\n<h4 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Horizontal-Flow\"><\/span>Horizontal Flow<span class=\"ez-toc-section-end\"><\/span><\/h4>\n<p style=\"text-align: justify;\">Consider the solid profile, shown in figure below consisting of n number of layers with H<sub>1<\/sub>, H<sub>2<\/sub>, H<sub>3<\/sub> &#8230;. H<sub>n<\/sub> in<br \/>\nthickness with their permeability k<sub>1<\/sub>, k<sub>2<\/sub>, k<sub>3<\/sub> &#8230;&#8230; k<sub>n<\/sub> respectively.<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-3509 size-full aligncenter\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/horizontal-flow.jpg\" alt=\"Horizontal Flow\" width=\"620\" height=\"367\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/09\/horizontal-flow.jpg 620w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/09\/horizontal-flow-300x178.jpg 300w\" sizes=\"auto, (max-width: 620px) 100vw, 620px\" \/><\/p>\n<h4 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Vertical-Flow\"><\/span>Vertical Flow<span class=\"ez-toc-section-end\"><\/span><\/h4>\n<p style=\"text-align: justify;\">In this case, flow takes place in the direction perpendicular to the stratification.<br \/>\nIn this case, to satisfy the continuity condition,<\/p>\n<p style=\"text-align: justify;\">q = q<sub>1<\/sub> = q<sub>2<\/sub> = q<sub>3<\/sub> = q<sub>4<\/sub> = &#8230;. q<sub>n<\/sub><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-3512 size-full aligncenter\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/vertical-flow.jpg\" alt=\"Vertical Flow\" width=\"635\" height=\"384\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/09\/vertical-flow.jpg 635w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/09\/vertical-flow-300x181.jpg 300w\" sizes=\"auto, (max-width: 635px) 100vw, 635px\" \/><\/p>\n<p style=\"text-align: center;\"><a class=\"btn btn-danger\" role=\"button\" href=\"https:\/\/study.madeeasy.in\/ce\/soil-mechanics-foundation-engineering\/effective-stresses\/\" target=\"_blank\" rel=\"noopener\">&lt;&lt; Previous<\/a> | <a class=\"btn btn-success\" role=\"button\" href=\"https:\/\/study.madeeasy.in\/ce\/soil-mechanics-foundation-engineering\/seepage-pressure\/\" target=\"_blank\" rel=\"noopener\"> Next &gt;&gt;<\/a><br \/>\n<strong> Must Read: <\/strong> <a href=\"https:\/\/study.madeeasy.in\/ce\/soil-mechanics-and-foundation-engineering\/\" target=\"_blank\" rel=\"noopener\"><strong>Soil Mechanics and Foundation Engineering<\/strong><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Soil is a particulate material and has pores that provides a passage for water. Such passages vary in size and<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[957,2],"tags":[981,978,980,979],"class_list":["post-3505","post","type-post","status-publish","format-standard","hentry","category-soil-mechanics-foundation-engineering","category-ce","tag-degree-of-saturation","tag-horizontal-flow","tag-kaolinite","tag-kozney-carman"],"_links":{"self":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/3505","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/comments?post=3505"}],"version-history":[{"count":0,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/3505\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/media?parent=3505"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/categories?post=3505"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/tags?post=3505"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}