Evaluation of the Suitability of Lateritic Soil of Jimma Zone as Road Construction Materials

Abstract

Lateritic soils are highly weathered and altered residual soils reach in secondary oxides of iron, aluminum, or both formed by the in-situ weathering and decomposition of parent rocks under tropical and sub tropical regions with hot, humid climatic conditions. Their formation process involves the leaching out free silica and base and accumulation of oxides of iron, aluminum oxide or both. Due to the presence of iron oxides lateritic soils are red in color. Geotechnical investigation is one of the effective means of detecting and solving pre and post construction problems. The Geotechnical properties of lateritic soils and their suitability for road construction have been evaluated for selected site in Jimma zone, Oromiya, Ethiopia. The principal purpose of this investigation is to obtained the geotechnical properties of lateritic soil of Jimma zone with aim of providing a valuable data base for emerging road construction which hasten the development of the country in order to support poverty reduction measure that have been taking place in the country, a total of twenty seven (27) samples at depth of 1.0 to 3.0 m after removing overburden soil at different pre-treatment condition were collected from nine( 9) different locations in the zone namely Agaro, Jimma ,Serbo, Limu, Sokoru, Babu, Yebu, Seka and Dedo. All the analysis were carried out in accordance with the standard given by ASTM testing procedures The soil specimens were tested at different sample preparation prior to testing. The research will be conducted by using both descriptive and analytical methods the test carried out on the soil sample includes geochemical test which are X-Ray Diffraction chemical tests as well as engineering property test which include moisture content, specific gravity, grain size analysis, Atterberg limit test, compaction and California Bearing ratio. Lateritic soil sample of Sokoru have been poor to fair in their properties and satisfy the criteria for sub grade only; Samples from Agaro, Seka & Dedo are fair in their properties and used for sub grade and lateritic soil samples from Jimma, Serbo, Limu ,Babu & Yebu are good in their general properties and used for base & sub base according to Bowls and using Ethiopian Road Authority Design Manual the lateritic soil samples of Agaro ,Sokoru and Seka satisfy the condition for poor value as sub grade ; lateritic soil samples of Serbo, Limu, Babu & Limu satisfy good as sub grade materials & lateritic soil sample of Jimma only satisfy good to excellent as sub grade materials as sub grade materials from the calculated value. In order to use the lateritic which are widely distributed in Ethiopia as materials in road construction proper selection criteria should be used .The use of lateritic soil for road construction has been done using the in appropriate specifications, i.e. those developed for the climate conditions of Europe and North America .It is clear that in order to reduce the wastage of a valuable resource many countries has been prepared their own specification. Therefore it is suggested that a detailed investigation to be carried out and the specifications (selection criteria) adapted for lateritic soil of Jimma zone as road construction materials.