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 carrie d out on an arid site containing gypsum lenses. This site was intended for the construction of an international airport in southern Israel, near the c ity of Eilat. Together with conventional in situ tests, special laboratory tests, such as: (a) loss of weight following protracted wetting; and (b) se ttlements under a constant vertical stress and prolonged wetting, were cond ucted on undisturbed gypsum and gypsum-rich specimens in order to assess th e engineering significance of the presence of gypsum and other salts in the sub-soil strata in the performance of pavements. The findings indicate tha t the wetting process of these materials constitutes a critical factor with regard to: (a) future settlement following the solubility of the gypsum le nses; 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. Th us, those values, rather than the strength values of the natural or the com pacted subgrade, or even the negative effects of the presence of gypsum, be come the critical parameters in the pavement-design process. (C) 1998 Elsev ier Science B.V. All rights reserved.