![\"Shear](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/mohr-failure-1-e1725434742608.jpg\")
<\/p>\n
MOHR FAILURE CRITERION<\/h2>\n\n- Mohr failure theory is based on the hypothesis that materials fails when the shear stress on the failure plane at failure plane reaches a value which is a unique function of the normal stress on the plane. i.e.,
\n\u03c4ff<\/sub> = f(\u03c3ff<\/sub>)
\nwhere, \u03c4 = shear stress and \u03c3 = normal stress; the first subscript refers to \u2018failure plane\u2019 and the second subscript denotes \u2019at failure\u2019.<\/li>\n<\/ul>\n![\"Mohr](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/mohr-failure-e1725434627590.jpg\")
<\/p>\n
\n- From data of different tests we can have a series of Mohr\u2019s circles. A line tangential to the Mohr circle gives a curve called Mohr failure envelope. It expresses the Functional Form of relationship between shear stress on failure plane at failure and normal stress on failure plane at failure.<\/li>\n
- If Mohr circle lies below the failure envelope (circle-I), every plane passing through this point has a shearing stress which is smaller than the shearing strength; this is known as stable condition.<\/li>\n
- Mohr circle lying above the envelope, (circle-II) cannot exist because it is not possible for the shear stress to exceed the shearing strength.<\/li>\n
- Any Mohr circle whose tangent is the Mohr failure envelope, represents a condition where in the point of tangency gives the stress conditions on the failure plane at failure.<\/li>\n<\/ul>\n
![\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/mohr-circle.jpg\")
<\/p>\n
FACTORS AFFECTING SHEAR STRENGTH<\/h3>\n
Some of the factors affecting shear strength of soil are:<\/p>\n
(a) Confining Stress:<\/strong>
\n(b) Drainage Conditions:<\/strong><\/h4>\n\n- It has been pointed out earlier that effective stress governs the shearing strength of soil.<\/li>\n<\/ul>\n
![\"Confining](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/confining-stress.jpg\")
<\/p>\n
\n- Drained condition occurs when the excess pore water pressure developed during loading of a soil dissipates i.e. \u2206u = 0<\/li>\n
- Undrained conditions occurs when the excess pore water pressure is not drained from the soil. i.e., \u2206u \u2260 0.<\/li>\n
- The existence of either condition\u2013drained or undrained depends on the soil type, geological formation (fissures, sand layer in clays etc.), and the rate of loading.<\/li>\n
- The values of shear strength parameters depends on the drainage conditions in saturated soils.<\/li>\n<\/ul>\n
\u03c6 = \u03c6\u2032 in case of drained test
\n\u03c6 = 0 in case of an undrained test<\/p>\n
(c) Density Index:<\/strong><\/h4>\n\n- The most important factor affecting the shear strength of granular soil is density index.<\/li>\n
- For the same composition of the soil, higher the density, higher the angle of friction. Hence higher will be the shear strength.<\/li>\n<\/ul>\n
![\"Density](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/density-index-e1725435158271.jpg\")
<\/p>\n
(d) Water Content and Saturation:<\/h4>\n\n- In case of fine grained soils, cohesion between soil particles is inversely proportional to water content.<\/li>\n
- The degree of saturation also affects the cohesion and the cohesion increases water content upto an optimum value above which it decreases with increasing water content for a given void ratio.<\/li>\n
- On the other hand, in unsaturated soils negative excess pore water pressure increases the effective stress
\n(\u03c3 = \u03c3 \u2013 u). Thus, if the pore water pressure is negative, the effective stress increases.<\/li>\n<\/ul>\n![\"Saturation\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/density-index-1-e1725435276574.jpg\")
<\/p>\n
(e) Composition and Particle Characteristics:<\/h4>\n\n- Angle of internal friction depends on grading of the soil. A well graded soil with high uniformity coefficient has a higher angle of friction as compared to poorly graded (i.e. uniform) soil.<\/li>\n
- Similarly, sharp angular grains which can interlock well with adjacent grain will show higher friction angles. Hence, minerals such as mica and flaky particles will show low angles of internal friction.<\/li>\n<\/ul>\n
<< Previous<\/a> | Next >><\/a>
\n Must Read: <\/strong> Soil Mechanics and Foundation Engineering<\/strong><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"\u2018Shear strength\u2019 is the resistance offered by soil against shear deformation, its value is equal to the shear stress on<\/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":[1002,1003,1001,1004],"class_list":["post-3574","post","type-post","status-publish","format-standard","hentry","category-soil-mechanics-foundation-engineering","category-ce","tag-confining-stress","tag-drainage-conditions","tag-mohr-failure","tag-mohr-failure-theory"],"_links":{"self":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/3574","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=3574"}],"version-history":[{"count":0,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/3574\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/media?parent=3574"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/categories?post=3574"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/tags?post=3574"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\n\u03c4ff<\/sub> = f(\u03c3ff<\/sub>)
\nwhere, \u03c4 = shear stress and \u03c3 = normal stress; the first subscript refers to \u2018failure plane\u2019 and the second subscript denotes \u2019at failure\u2019.<\/li>\n<\/ul>\n
<\/p>\n
- \n
- From data of different tests we can have a series of Mohr\u2019s circles. A line tangential to the Mohr circle gives a curve called Mohr failure envelope. It expresses the Functional Form of relationship between shear stress on failure plane at failure and normal stress on failure plane at failure.<\/li>\n
- If Mohr circle lies below the failure envelope (circle-I), every plane passing through this point has a shearing stress which is smaller than the shearing strength; this is known as stable condition.<\/li>\n
- Mohr circle lying above the envelope, (circle-II) cannot exist because it is not possible for the shear stress to exceed the shearing strength.<\/li>\n
- Any Mohr circle whose tangent is the Mohr failure envelope, represents a condition where in the point of tangency gives the stress conditions on the failure plane at failure.<\/li>\n<\/ul>\n<\/p>\n
FACTORS AFFECTING SHEAR STRENGTH<\/h3>\n
Some of the factors affecting shear strength of soil are:<\/p>\n
(a) Confining Stress:<\/strong>
\n(b) Drainage Conditions:<\/strong><\/h4>\n- \n
- It has been pointed out earlier that effective stress governs the shearing strength of soil.<\/li>\n<\/ul>\n<\/p>\n
- \n
- Drained condition occurs when the excess pore water pressure developed during loading of a soil dissipates i.e. \u2206u = 0<\/li>\n
- Undrained conditions occurs when the excess pore water pressure is not drained from the soil. i.e., \u2206u \u2260 0.<\/li>\n
- The existence of either condition\u2013drained or undrained depends on the soil type, geological formation (fissures, sand layer in clays etc.), and the rate of loading.<\/li>\n
- The values of shear strength parameters depends on the drainage conditions in saturated soils.<\/li>\n<\/ul>\n
\u03c6 = \u03c6\u2032 in case of drained test
\n\u03c6 = 0 in case of an undrained test<\/p>\n(c) Density Index:<\/strong><\/h4>\n
- \n
- The most important factor affecting the shear strength of granular soil is density index.<\/li>\n
- For the same composition of the soil, higher the density, higher the angle of friction. Hence higher will be the shear strength.<\/li>\n<\/ul>\n<\/p>\n
(d) Water Content and Saturation:<\/h4>\n
- \n
- In case of fine grained soils, cohesion between soil particles is inversely proportional to water content.<\/li>\n
- The degree of saturation also affects the cohesion and the cohesion increases water content upto an optimum value above which it decreases with increasing water content for a given void ratio.<\/li>\n
- On the other hand, in unsaturated soils negative excess pore water pressure increases the effective stress
\n(\u03c3 = \u03c3 \u2013 u). Thus, if the pore water pressure is negative, the effective stress increases.<\/li>\n<\/ul>\n<\/p>\n(e) Composition and Particle Characteristics:<\/h4>\n
- \n
- Angle of internal friction depends on grading of the soil. A well graded soil with high uniformity coefficient has a higher angle of friction as compared to poorly graded (i.e. uniform) soil.<\/li>\n
- Similarly, sharp angular grains which can interlock well with adjacent grain will show higher friction angles. Hence, minerals such as mica and flaky particles will show low angles of internal friction.<\/li>\n<\/ul>\n
<< Previous<\/a> | Next >><\/a>
\n Must Read: <\/strong> Soil Mechanics and Foundation Engineering<\/strong><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"\u2018Shear strength\u2019 is the resistance offered by soil against shear deformation, its value is equal to the shear stress on<\/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":[1002,1003,1001,1004],"class_list":["post-3574","post","type-post","status-publish","format-standard","hentry","category-soil-mechanics-foundation-engineering","category-ce","tag-confining-stress","tag-drainage-conditions","tag-mohr-failure","tag-mohr-failure-theory"],"_links":{"self":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/3574","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=3574"}],"version-history":[{"count":0,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/3574\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/media?parent=3574"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/categories?post=3574"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/tags?post=3574"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
- It has been pointed out earlier that effective stress governs the shearing strength of soil.<\/li>\n<\/ul>\n