Evaluation on Prevailing Pavement Layers Strength using Destructive Test at Distressed Section along Dembi- Bedelle Highway

Abstract

Pavement distresses are one of the major problems in developing countries and the wide range of problems that occurred on sealed road. While the problems can be occurred on going or after construction of the road has been finished. Broadly speaking, flexible pavement distresses fall into different categories:Cracking,Patching. Surface Deformation, Surface Defects, Potholes and Miscellaneous Distresses. This research study carried out at Ilu-Ababor zone situated within the Western Ethiopia. This place is found in Western Oromia region. Dembi-Bedele highway currently shows pothole, patching, rutting, polished aggregate, cracks and shoving types of distress. The scope of the research is to determine the type, extent and severity of the pavement distresses and to measure the structural strength of the existing road pavements at distressed sections. Destructive test method (DCP and Test Pits) were used in the field and laboratory testing tools for the data analysis. Basically, six different data were collected by DCP test and three test pits have been taken. Besides, DCP field data collected were analysed by UK DCP, 3.1 software. From these results,CBR value, pavement layers thickness and structural strength of the pavement were known. Purposive sampling techniques used for DCP test and Test Pits at both distressed and normal section. Base on the DCP data analysis, thickness ofsurface,base course sub base sub grade layers decreased by 25mm, 31mm, 95mm respectively on (chainage 17+870).Additionally, the CBR values of base course, sub base and sub grade are 78%, 44% and 39% respectivel y. These results are less than the standard.Besides, at (chainage 25+100) the thickness of pavement surface, base course, sub base and sub grade layers decreased by 10mm, 18mm, 104mm and 47mm respectively.When compared with previous design. The CBR values are 62%, 27% and 21% for base course, sub abse and sub grade respectively.