Thermo-hydro-mechanical behaviour of Kaolin clay

Abstract

The need for an improved understanding of the effects of temperature on the hydro-mechanical behaviour of compacted clays is important in many applications, such as disposal of high level nuclear wastes, burial of high voltage cables, drilling of deep offshore wells, and clay liners used on landfills. In this thesis, a study of the thermo-hydro-mechanical (THM) behaviour of kaolin clay under different conditions is presented. A series of experimental unsaturated tests was carried out, including temperature and suction controlled oedometer tests, and suction measurements to obtain the soil water retention curves at different temperatures. In order to describe the dependency of the soil water retention curves on temperature, the influences of temperature on the contact angle of menisci and the microstructure of the soil samples were studied. Moreover, Environmental Scanning Electron Microscopy was employed for studying the microstructure of the soil at certain conditions of interest. A new suction and temperature controlled oedometer cell was designed, developed and calibrated for investigating THM behaviour of kaolin clay. The oedometer was used to examine the combined effects of suction and temperature on compressibility and collapse behaviour of the soil. In this thesis, special attention was given to the filter paper methodology for suction measurements at different temperatures. The calibration curve of Whatman No. 42 filter paper was determined at 10, 25 and 50ºC using the vapour equilibrium technique with sodium chloride solutions at different concentrations and the axis translation technique. Based on the experimental data, a unique calibration equation was proposed; taking into account the effect of temperature. The experimental results showed that temperature has a relevant influence on filter paper suction measurement and that misleading results can be obtained if temperature is not taken into account in the calibration equation.