Keynote lecture: The geotechnical behaviour of arid and semi-arid zone soils Southern African experience

Water tables in arid climatic zones are usually deep, and the soils are predominantly unsaturated. After describing the stress variables that control the behaviour of unsaturated soils, this paper considers two of the main problems associated with arid zone soils, namely the heave of deep expansive clays and the collapse of windblown sands. Much is known of these two problems, but, as the paper will show, much remains to be learned.