Cost-Comparison Analysis of Lime Stabilization versus Replacement of Expansive Soil (A case study of Aseb-Beri Loat1 Road Project)

Abstract

Expansive soils are soils that have a property of large volumetric changes, both shrinkage and swell, due to variations in their moisture content. Their bearing capacity is poor. For road to be constructed on such soils, the subgrade should be designed to minimize subsequent changes in moisture content and consequent volume changes thereby improving bearing capacity of the soil. The subgrade material for road construction within the project of Aseb-Bari lot1 road project, located in Botar Tolay Wereda, is highly dominated with such types of expansive soils. An appreciable part of Ethiopia is covered by expansive soil. Most of the roads constructed and proposed as well as substantial amount of the newly planned railway routes in the country traverses across expansive soils. The roads on this type of soils fail before their expected design life, in some cases after few months of completion. The subgrade material for road construction within Aseb-Bari lot1 road project, located in Botar Tolay Wereda, is highly dominated with such types of expansive soils. The methods applied to improve the engineering property of such soil were either to stabilize the existing soil or to replace the soil with non-expansive impermeable soil to the depth affected by seasonal moisture changes. In the present research work, the economic advantage of improving the expansive soil with hydrated lime to that of replacement of expansive soil with material having good strength was investigated. For the comparison purpose, first characterization of the native soil and the stabilized subgrade was carried out. The cost estimated for expansive soil stabilization by hydrated lime within 1km road was 1,935,618 ETB and the cost estimated for replacement was 2,089,049.60ETB. The comparison shows that the cost of expansive soil stabilization by hydrated lime was less than the cost of expansive soil replacement by 7.3%. This result shows that stabilization of expansive subgrade soil with hydrated lime is more economical as compared to replacement of expansive subgrade soil for pavement construction.