EFFECT OF DEGREE OF SATURATION ON CONSISTENCY OF FINE GRAINED SOILS

Abstract

Dr. Terzaghi in his James Forrest Lecture givento the Institution of,Civil Engineers in London in May 1939.used the following phrase, 'On a planet without any water there would be no need for soil mechanics' In case of shallow foundations on fine grained soils, changes of water content may produce in the foundation soil volume changes detrimental to the structure or significant deterioration in the bearing capacity. Thus varia-tion in water content varies the properties of fine grained soils to a great extent. But since one performs field tests at one particular moisture content, that is, field moisture content, it becomes necessary to know quantitively the variation in stren-gth with water content so that designer can incorporate it in the design of foundation, if there is any possibility of mois-ture content variation in the sub soil during the life time of the structure, Therefore, in this dissertation an attempt has been made to study the variation of soil properties - unconfined compressive strength, shear strength and cone bearing value with the varia-tion .in moisture content in silts and clays. To carry out this study silts and clays of low,medium and high compressibility were taken directly from the field in the form of undisturbed chunk samples. On these undisturbed samples unconfined compression test, vane shear test and North Dakota Cone tests were performed in three different conditions, that is, natural condition, satura-ted condition and dry condition. Based on the data obtained from an extensive laboratory. testing programme carried out on undtsturbed samples, curves have been given showing the effect of degree of saturation and plag-ticity data on unconfined compressive strength, vane shear stren-gth and the cone bearing pressur