STUDIES ON THE SWELLING BEHAVIOUR OF GWALIOR BLACK COTTON SOIL

Abstract

Expansive soils, though primarily belonging to the fine- grained group of soils and are classified mostly as clay, have assumed significant importance in foundation engineering due to their characteristic and often detrimental behaviour of volume changes which accompany the ingress of water into them or the loss of water from them. In this investigation, the percentage swelling and the swelling pressure of the Gwalior back cotton soil has been studied both without and with sand or fly-ash admixture. Further, to analyse the anisotropic swelling behaviour, samples were tested with their orientation at angles of 0°, 22.5°,45°,67.5° and 90° measured from the vertical. These samples had been comacted as per 1.3.(Light compaction) procedure at optimum moisture content in view of its practical importance in the field. Out of the several methods of measuring the swelling behaviour of clay, the variable volume method has been used in the present study to measure the swelling and swelling pressure of the soils. The results have showed that the directional variation of swelling and swelling pressure is of an elliptical nature, with the major axis oriented at 45° to vertical, indicating maximum swelling in this direction. While fly-ash admixture was found to have practically no effect on the swelling behaviour, addition of sand was found to have a significant influence in reducing the swelling and swelling pressure.