Investigation of the Performance of Unsealed Road Sub Base Materials Used as Wearing Course of Gravel Road (In the Case of Kamashi –Yaso Road)

No Thumbnail Available



Journal Title

Journal ISSN

Volume Title


Addis Ababa University


A good road structure may help in reducing the number of accidents. Wearing course is the top layer of the road structure which is the layer exposed to the vehicle tyre and environment. The international roughness index and Present Serviceability Index are both indices that can be used as indicator of road roughness and serviceability. Objective of the study is primarily to determine the performance and the durability, serviceability and service life of unsealed gravel road wearing course above sub grade. In evaluating the serviceability of the road, roughness is an important indicator of pavement riding comfort and safety. It is condition indicator that should be carefully considered when evaluating pavement performance. At the same time, the use of roughness measurements plays a critical role in the pavement management system. There are many devices used for roughness evaluation. In this thesis, roughness measurement was done by Merlin manual instrument. The methodology used to carry out the thesis work is carry the field data measurement for roughness and gathering user assessment for the case study site and taking sample data of soil for strength test of CBR. International roughness index was measured by using Merlin roughness index measuring instrument. And used for calculating present serviceability index as independent parameter. Both international roughness index and present serviceability index were measured along 200m section of the road for about 19.7km of the study route. This studies only focuses on one type of road which was gravel pavement located on western part of Ethiopia in Benishagul Gumuz regional state in Kamashi Zonal state. The work has generated that this unsealed gravel road is running with in the design limit without sever deterioration as the result of serviceability, user assessment, CBR strength test and roughness value shows.



Road and Transport Engineering