Application of Dispersive Soils as a Sub Grade and Embankment Materials (Case Study on Adama – Awash Railway Section)
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Date
2016-04-27
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Addis Ababa University
Abstract
Dispersive soils are prevalent in many areas of Ethiopia (especially in the rift valley). The use of dispersive soils in embankment structure can lead to serious engineering problems if the soil is not accurately identified before use and appropriate mitigation measures are not taken. The current tests used for identification include pinhole, double hydrometer, crumb and chemical tests.
The main objective of this research is to use dispersive soil as an alternative embankment construction material. The light greyish sub grade soil of the pilot – study area (Adama – Welenchity section) have been tested with all identification tests of dispersive soil to check the extent of dispresivity of the soil. According to the result, the sub grade soil is dispersive with Pinhole test D2 (dispersive soil category 2), double hydrometer percent dispersion value TP1=87.17% and TP2=83.24%, crumb test result of grade 3 and Chemical analysis exchangeable sodium percentage of 31.93%.
Treatments to dispersive clay using gypsum was carried out in this study. The optimum amount of gypsum required to treat a dispersive clay sample was 5%. The identification test results obtained by stabilizing with 5% recycled gypsum are: - double hydrometer percent dispersion value 24.72%, pinhole test ND1 (non-dispersive soil 1) and chemical analysis exchangeable sodium percentage of 6.54%. The engineering index tests of the dispersive soil have also been checked and found that the dispersive soil qualifies the specification requirement of embankment construction materials. After being treated with 5% recycled gypsum the dispersive soil can be used for embankment construction.
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Embankment Materials, Dispersive Soils, Sub Grade