Flexible pavements are composed of asphaltic layer, base course; sub base materials which laid over a well compacted and strong sub grade foundation soil. Basic engineering properties of Sub grade materials are required for design and Coarse grained soils serves as good for supporting pavements whereas fine grained soils, particularly clayey soils pose problem to pavement. Jimma town is a big trade center and coffee production areas of in Ethiopia but, the current existing condition most parts of the road are deteriorated. The objective of this research was to investigate effects of subgrade and sub-base materials quality on flexible pavement. The distress is categorized by level of severity according to Ethiopian Roads Authority (ERA) standard specification to get 4-stations high deterioration of block crack, 6-stations medium deterioration of Alligator crack and 5-stations low deterioration of edge crack of the studied stretch along Ajip to Gebrel church of 10 km in Jimma town. The samples taken randomly from the deteriorated area of the subgrade and sub-base materials of 15 stations and laboratory tests conducted and also the results were discussed, compared with the ERA, AASHTO and ASTM. The tests result NMC>OMC indicated that excess water in the subgrade and sub-base materials according to AASHTO D-180 specification, compaction of subgrade and sub-base layers are below the minimum requirement (MDD>97% laboratory density) of AASHTO, poor strength (CBR<1.76gm/cc) of AASHTO T-193 and ERA specification, sieve analysis for gradation out of the upper and lower limit of AASHTO T-27 for the subgrade and sub-base materials. These can be causes of pavement deterioration on flexible pavement. But, the Atterberg’s limit test results satisfy the standard specification of ASTM D-4318. From this research recommended that the designer and contractor should be follow the minimum requirement set by standard specification regarding the engineering properties of materials, the side ditch must be constructed so as to prevent infiltration of water to the under lining strata, seal coats shall be applied to prevent infiltration of water through cracked surfaces to subgrade layer of the pavement.
Deterioration, Distress, Moisture Content, Pavement, Sub-base and Subgrade
International Journal of Trend in Scientific Research and Development - IJTSRD having
online ISSN 2456-6470. IJTSRD is a leading Open Access, Peer-Reviewed International
Journal which provides rapid publication of your research articles and aims to promote
the theory and practice along with knowledge sharing between researchers, developers,
engineers, students, and practitioners working in and around the world in many areas
like Sciences, Technology, Innovation, Engineering, Agriculture, Management and
many more and it is recommended by all Universities, review articles and short communications
in all subjects. IJTSRD running an International Journal who are proving quality
publication of peer reviewed and refereed international journals from diverse fields
that emphasizes new research, development and their applications. IJTSRD provides
an online access to exchange your research work, technical notes & surveying results
among professionals throughout the world in e-journals. IJTSRD is a fastest growing
and dynamic professional organization. The aim of this organization is to provide
access not only to world class research resources, but through its professionals
aim to bring in a significant transformation in the real of open access journals
and online publishing.