Relation between Shrinkage Index and Swelling Pressure for Expansive Soil found in Addis Ababa

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Addis Ababa University


This research is inspired by the PhD thesis work of H. B. Nagaraj from Indian Institute of Science titled “Prediction of Engineering Properties of Fine Grained Soils from their Index Properties”. The PhD thesis indicated that the swelling pressure has a poor correlation with the liquid limit, a good correlation with the plasticity index and a better correlation with the shrinkage index (liquid limit – shrinkage limit) of fine-grained soils. Nagaraj used a total set of ten remolded soil samples representing the three extreme clay mineral types namely Kaolinite, Illite and Montmorillonite. Also due attention was given to select pairs of soils with nearly the same liquid limit values, but having different plasticity properties. Consequently, the research title “Relationship between Shrinkage Index and Swelling pressure for expansive soil found in Addis Ababa” was selected for this Master’s thesis work. In contrast to the PhD work mentioned above, the results of this Masters study show that the relationship between the swelling pressure and the shrinkage index for Addis Ababa expansive clay (one type of soil) is very weak. However, a good approximation is obtained between the normalized shrinkage index (normalized by initial moisture content) and the swelling pressure with R2 value of 0.89. In addition to this, a better estimation is observed when multiple soil parameters are involved in different combination in prediction of the swelling pressure rather than only the shrinkage index. The correlations developed in this work are compared with previously established equations such as David and Komornik (1969), Nayak and Christensen (1974), Daniel Teklu (2004), Vijayvergiya and Ghazzaly (1973), where the first two equations were found to be in a better agreement with the correlations developed in this work.



Swelling Pressure, Shrinkage, Expansive Soil