Site investigation of sub-soil with gypsum lenses for runway construction in an arid zone in Southern Israel

This paper presents several highlights from a subgrade investigation carried out on an arid site containing gypsum lenses. This site was intended for the construction of an international airport in southern Israel, near the city of Eilat. Together with conventional in situ tests, special laboratory tests, such as: (a) loss of weight following protracted wetting; and (b) settlements under a constant vertical stress and prolonged wetting, were conducted on undisturbed gypsum and gypsum-rich specimens in order to assess the engineering significance of the presence of gypsum and other salts in the sub-soil strata in the performance of pavements. The findings indicate that the wetting process of these materials constitutes a critical factor with regard to: (a) future settlement following the solubility of the gypsum lenses; and (b) the decrease in the strength of the subsoil. This study also showed that very low values of in situ densities characterize this area. Thus, those values, rather than the strength values of the natural or the compacted subgrade, or even the negative effects of the presence of gypsum, become the critical parameters in the pavement-design process.