Correlating Liquidity Index with Vane-shear Strength of Clays in Addis Ababa
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Date
2017-10
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Addis Ababa University
Abstract
Investigation of soil properties is one of the main tasks of Geotechnical Engineer. Soil testing methods don’t require the same amount of time and effort; even some of the apparatus are scarce in developing countries. This usually leads to unreliable and impractical test results. That is why it is important to develop empirical equations that fit the local area.
In this thesis, attempts have been made to obtain valid correlations between undrained shear strength and liquidity index. For this purpose, 6 disturbed samples were collected from 5 sites (from depth of 1m to 3m) and for each sample Atterberg limit and standard compaction tests were conducted. Beside that by remolding these samples 12 vane shear tests for each of the samples in total 72 vane shear tests were conducted. From these tests undrained shear strength and liquidity index are determined.
For the analysis, SPSS and EXCEL softwares have been used for the best fit line, correlation, regression analysis and comparative study. Equations were developed for each soil sample with a very strong correlation of coefficient of determination (R2) values ranging from 0.927 up to 0.991. From the result it has been shown that the use of the commonly assumed 100-fold factor increase in strength from the liquid limit to plastic limit over predicts the measured data of the soil strength. In this study the ratio factor fold in strength is between 30 up to 63. The results are expected to have wide application in the construction sector for soft clays.
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Keywords
Vane-Shear, Correlating Liquidity Index, Strength of Clays