Practical Problems of Highway Construction in Black Cotton Soil Areas and In-Place Remedial Measures: A Case Study
Dr. S.S.Seehra, Chief Pavement Specialist–cum–Materials and Geotechnical Engineer, Span Consultants Pvt. Ltd. (Member of the SNC–LAVALIN Group Inc.) and (Former Director–Grade Scientist and Head, Rigid Pavements Division, CRRI), New Delhi.
Black cotton soils are inorganic clays of medium to high compressibility and form a major soil group in India. They are characterized by high shrinkage and swelling properties. This Black cotton soils occurs mostly in the central and western parts and covers approximately 20% of the total area of India. Because of its high swelling and shrinkage characteristics, the Black cotton soils (BC soils) has been a challenge to the highway engineers. The Black cotton soils is very hard when dry, but loses its strength completely when in wet condition.
It is observed that on drying, the black cotton soil develops cracks of varying depth. Figure 1 shows the typical cracks in Black cotton soils (BC soils) in a dried state. As a result of wetting and drying process, vertical movement takes place in the soil mass. All these movements lead to failure of pavement, in the form of settlement, heavy depression, cracking and unevenness. This article covers highway construction in Black cotton soils (BC soils) and also describes a case history of highway construction in highway construction in Black cotton soils.
