GEOTECHNICAL INVESTIGATION ON CAUSES OF ROAD FAILURE OF DODOLA –GOBA ASPHALT ROAD PROJECT AND THEIR REMEDIAL MEASURES

Abstract

Dodola – Goba asphalt road, found in South East Ethiopia, was prematurely failed before serving its design life. From total stretch (130km) of the project, this study focus and detail investigations has been carried out on Adaba -Dinsho road section which was failed critically within 3 (three) years after it has been opened for traffic. A number of maintenance had been performed to make the road passable, but each maintained sections are failing with in short period. In this study, the real cause of the road failures has been identified and proper remedial measurements for failed section has been proposed. To asses this, field and laboratory investigations which includes visual inspection, field test, physical measurements and laboratory tests to determine geotechnical properties of sub grade, sub base and base course materials by comparison of the materials quality as per ERA 2014 and/or AASHTO design manuals were carried out. Finally based on the investigation, presence of too much moisture content on sub grade and pavement materials due to improper design and late maintenance of drainage, improper geometrical design, moisture sensitive geology/soil and seasonal variation of ground water are the major factors of failures. Also poor geotechnical properties of road base and sub base of materials due to substandard material quality and improper construction methods are the major causes of road failures. Correcting drainage system and geometric design of the road and reconstruction of pavement layers by standard material quality and methods are the proper remedial measure for failed section