Premature distress of a pavement on expansive black cotton soil in the Horn of Africa

Abstract

This paper discusses a typical example of the distress experienced by a flexible pavement constructed over black clay soil, also commonly known as black cotton soil, where minimal precautionary measures were implemented. Black cotton soils are generally recognized as expansive soils and change significantly in volume with changes in the moisture condition due to wetting-up and drying-out during the wet and dry seasons respectively. The volume changes lead to differential deformation which then induces distress and leads to damage of the pavement constructed on such soils. By way of example the paper describes an investigation of a road in the Horn of Africa in an area with extensive deposits of the black clays, demonstrating the importance of correctly characterizing these soils prior to the pavement design and taking appropriate counter measures against expected movement of the roadbed that will cause damage to the pavement