An Experimental Study on Leaching in Gypseous Soil Subjected to Triaxial Loading

Gypseous soil is one of the important high salt content soils in aired and semiarid areas. The failure problems of this soil occur due to the softening of soil and the dissolution of gypsum during leaching (if the flow is continuous). A significant lack of knowledge existed in this research area regarding the effects of leaching on the engineering properties and behavior of gypseous soil in both natural and treated conditions. In this paper, a series of consolidated drained triaxial permeability-leaching tests, under isotropic compression considering three confining pressures (i.e. 100, 200 and 300 kPa), has been carried out to study the effect of leaching on the geotechnical properties and behavior of gypseous soil. A high gypsum content sand soil with little fines was used in this study. Besides, dihydrate calcium chloride was used as an additive to improve the geotechnical properties of soil. The chemical additive percentages are 2.5% and 5.0% by weight of the dry soil. According to the test results, upon leaching, a large reduction in the cohesion of natural soil has been recorded, while the angle of internal friction approximately remained constant. Moreover, the natural soil became more compressible when subjected to leaching under isotropic condition. The inclusion of additive led to a reasonable reduction in permeability, leaching strain, and dissolution of gypsum, while, the shear strength parameters of treated soil were unaffected upon leaching.