Causes of Flexible Pavement Deterioration and Its Remedial Measures: A Case Study Bako to Nekemte Road section.

Abstract

Road constructing in Ethiopia is increasingly in demand to meet its medium and long term development programs. Roads are constructed radiating from the metropolis of Addis Ababa towards the Western direction. Some portions along the alignment proposed and existing roads traversed low resistance of the subgrade that affect the stability of upper layers of pavements. Structural deteriorations are observed on Flexible Pavements, would it be constructed by good quality or low quality of materials. Flexible pavement roads in Ethiopia often deteriorate in different ways, because of the harsh climatic conditions, lack of proper design and quality control, sudden increasing of traffic due to the construction of different industries, high loads and inadequate assessment for identifying causes of deteriorate before carrying out Maintenance and rehabilitation. Bako to Nekemte Project which was completed in 2013 observed there were deterioration that needs to be addressed and a corresponding remedial measures must be drawn. Hence, a desk study, letter correspondence review, field visual inspection and in-depth field investigation have been undertaken to identify the causes of flexible Pavement deterioration. A possible remedial measures had been organized for every observed failure or deterioration to obtain normal pavement condition of the study area. An investigation was made by using laboratory and field test to determine the adequacy of the underlain material to serve as a subgrade, sub base course and base course for road construction based on project specifications and Ethiopian Road Authority (ERA) Specification. The investigation covered field tests to determine the in-situ condition of the road materials while laboratory tests on representative samples were extracted from site to determine the engineering properties of soil materials and to compare test results with the existing conditions of pavement layers. From the field tests and laboratory tests carried out, it is observed that the causes of flexible pavement deterioration of this road section are mainly due to the inadequacy of existing thickness of the base layer for the current traffic loading, engineering properties of the pavement layers material, poor method of construction, poor design quality and lack of side drainage. To reduce more damage for this road section reconstruction of the base and providing proper drainage at the deteriorated sections must be required. Raveling, pumping, potholes, edge cracking and rutting are the most dominant type of deteriorations along Bako-Nekemte road section. It is expected that the results of this research will provide useful information about all causes of flexible pavement deteriorations and its remedial measures for the Bako-Nekemte road section.