ABSTRACT
Arid soils are unsaturated, heavily structured and often contain high concentrations of salts. The most critical aspect of engineering behaviour is normally the occurrence of swelling or collapse upon wetting. This, and many other features of mechanical behaviour, can be represented within an elasto-plastic framework for unsaturated soils. Whether the soil will swell or collapse upon wetting depends upon the in-situ stress state (in terms of net stress and suction), the reduction of suction caused by wetting and the current position of the yield curve (which is determined by the stress history and the presence of any bonding between particles). Arid soil behaviour should be set within the general context of unsaturated soil behaviour, but due consideration should be given to factors specific to arid environments (such as particular types of soil structure and the common occurrence of salts).
