Level Surveys and Patterns of Movement in Collapsible and Expansive Soils Studies

The demerits of level surveys for assessing foundation movements associated with moisture-induced volume change of soils have been well discussed and debated in the literature. In spite of the limitations of level surveys, and the associated strong desirability of benchmarked survey data for assessment of foundations movements on moisture sensitive soils, unbenchmarked level surveys continue to be used in forensic studies of buildings damaged by expansive and collapsible soils. The common uses and limitations of level survey data are briefly reviewed, and unbenchmarked level survey data are presented and discussed for three different cases of residential structures founded on collapsible and/or expansive clays. The level survey data are used, together with other available sources of information, in developing plausible explanations for building damage resulting from soil-wetting-induced differential movement of the structures.