Swelling behaviour of clay mixture

Abstract

Expansive soils have posed a problem to geotechnical engineers as they exert a swelling pressure on the surrounding foundation structures due to variations in moisture content of the soil. In this report, the expansive behaviour of swelling soil is investigated. Expansive soils have the potential for both shrinking and swelling under moisture variations (Nelson, 1992). In this study, only swelling is being studied. Swelling is a prevalent problem which causes structures that are being built on expansive soils to experience widespread damages due to the large uplift forces induced by the swelling effect. The swelling soil shows dilative behaviour and exerts swelling pressure to the surroundings when it absorbs water. To simulate the swelling soil, mixtures of clay consisting of Sodium-Bentonite and construction sand are used. Since soil properties probably have a significant effect on the swelling behaviour of the clay mixtures, we will investigate the effect of molding water content and percentages of bentonite on the swelling pressure and volume change of the clay mixtures. A mixture of construction sand and powdered sodium bentonite is being used for landfill materials commercially as it is more economical and most probably would not visibly crack when desiccated. Sand is a pervious material in nature. When bentonite is added, the hydraulic conductivity of the mixture is lowered. This lowered hydraulic conductivity makes it suitable to be used for landfill material as leakage of harmful gases and fluids can be prevented. When the water content is increased, the swelling of the clay mixture also decreases the shear strength of the mixture. The relationship between the swelling pressures and bentonite content can be used to predict the behaviour of similar expansive clays and preventive measures can be taken to ensure the robustness of structures built on such soil. A main concern is the impact of destruction of such soils to underground structures. Catastrophic accidents might occur if the dilation effects of swelling soils are ignored during the construction of these structures. Ignorance of the behaviour of these swelling soils is tantamount to neglecting the safety of occupants which reside within these structures.