Chapter 29: Arid Soils

Arid soils form in conditions where a water deficit (where mean annual losses through evapotranspiration exceed the mean annual volume of water entering the ground from precipitation) acts upon the soil. These soils can present several challenges to engineers due to the highly variable nature of their engineering properties, which are, in part, associated with active and ancient geomorphic processes. Arid soils can be unsaturated, cemented or uncemented, loose and poorly graded, and as a result can prove problematic to geotechnical engineering because of (but not limited to) metastable behaviour, significant shrink–swell or collapsing potentials, and/or aggressive salt environments that can weather man-made structures. Key to understanding how arid soils behave, and how these soils can be engineered, is achieved through an appreciation of the geomorphology of their formation and a suitable ground investigation. Once the ground conditions are understood, appropriate engineering assessments and interventions can be applied. Several other logistical challenges also occur with arid environments owing to the limited availability of suitable water sources for construction; through careful planning these problems can be avoided.