Problems in testing problematic expansive soils

Expansive soils are problematic to engineers and even more problematic to characterize by laboratory testing. This paper provides an overview of experiences in undertaking measurements and testing expansive soils. It first considers difficulties in obtaining representative samples of expansive soils, recognizing the need to test samples that are large enough to be representative of a coarsely cracked medium. In particular, the work recognizes the importance of structure, on both microscopic and macroscopic scales, and despite the recognized difficulties, it emphasizes the necessity of preserving structure in sampling and testing, to obtain meaningful results. Then, it considers the difficulties that arise in regard to simulating or controlling the boundary conditions that affect soil behaviour in real foundations. These are a complicated combination including water content, suction, volume change, swell pressure and strain. The paper illustrates these points with a series of brief descriptions of studies undertaken in expansive clay soils, where different approaches were adopted to achieve a variety of outcomes that promote our understanding of the soil's problematic nature