Laboratory and field swelling pressures of a black cotton soil

Abstract

The swelling pressure of a black cotton soil is investigated :n the project carried out for this thesis. Soil as one of the materials on the earths crust is introduced; its mineralogy and atomic properties are discussed. The solid phase in soil consist of crystals whose properties are discussed paying particular attention to the structure part of it. The minerals in soils could be non-clay or clay, their difference with respect to structure and behaviour are considered in the thesis. The classification of clay minerals into groups and the structural differences existing between the groups are also considered. Problems encountered in the building industry, from black cotton soil due its swelling properties are outlined in this thesis.The various factors that influence the swelling characteristics of soil black cotton are considered, and their interrelation and influence on each other are also discussed. When an engineer undertakes to design a project, there are field and laboratory investigations ,. to be carried out before construction starts.The absence of standard apparatus to measure swelling pressure of black cotton soil in the field called for the design and testing of appropriate equipment. The requirements for such equipment vary from site to site depending on both physical and environmental conditions. For this project a design was carried out to suit the local conditions. The equipments were fabricated, tested and calibrated as part of the research work, Laboratory swelling pressure of black cotton soil was measured on soil samples obtained from all the five identified sites. In order to carry out the laboratory swelling pressure tests and be able to relate the results obtained to those from the field data, sampling apparatus had to be designed and the laboratory swelling pressure apparatus had to be modified. The pressure obtained both in the field and in the laboratory were compared and it was found that the field swelling pressure were much less than the laboratory swelling pressures, regardless of whether the laboratory soil sample was disturbed or undisturbed.