Characteristics of Black Cotton Soil

About 3% - 5% of the world land area occupies Black Cotton Soil (BCS) and mainly found in Sudan, South Africa, Ethiopia and Tanzania. In Asia, they are found extensively in the Indian Decca Plateau. They also found in some parts of Australia, West Indies and Russia. Black cotton soils have varying colors 'ranging from light grey to dark grey and black. The black color in Black cotton soil (BC soil) is due to the presence of titanium oxide in small concentration. The Black cotton soil (BC soil) has a high percentage of clay, which is predominantly montmorillonite in structure with clay stones, sedimentary and residual soils. Foundation failures in these soils are attributed mainly to the differential movement of the structure as a result of uneven ground movements due to alternate swelling and shrinkage of the soil.This textbook guides the students on testing the characteristics of highly expansive black cotton soils of Ethiopia and presents some stability techniques using locally available ingredients for the society.