Soil with Na2SO4 is one of the special soils in salinized soils region in which engineering damages are usually produced, for example, airport in arid regions. Salt ions in soil–water solution are partly released and crystallized, and migrated from warm to cool areas and from wet to dried areas due to temperature difference and evaporation action; soil volume will be expanded to form salt expansion. Salinized soil results not only in salt expansion damage but also frost boil that produces large effect on engineering.

Salt expansion of fine grain soil has been studied and a lot of results are obtained in the past years. Qiu (1986) studied the processes of ion and water migration and proposed ion types of salt that frost heave restrained. Fei et al. (1994) studied salt expansion characteristics of Xi'an Loess and proposed that salt expansion ratio is minimum for soils with 3% Na2SO4 and 1.8 g/cm3 initial dried weight unit, and initial salt expansion of saline soil with Na2SO4 is a relationship of two parabola with initial dried weight unit and water content. Chen et al.,1988. X. Chen, G. Qiu and Y. Wang , On salt heave of saline soil. In: Proceedings of 5th International Symposium on Ground Freezing (1988), pp. 35–39 (In Chinese) . View Record in Scopus | Cited By in Scopus (0)Chen et al. (1988) proposed that salt expansion ratio of silt with Na2SO4 is decreased in exponential law with cooling speed and overburden load increasing. Xu and Xu systemically studied frost heave and salt expansion of soils from unfrozen water change, water and ion migration, salt expansion deformation, its effect factors, prediction model and so on, and obtained integrated research productions. Many researchers mainly studied some properties of saline soils such as strength and deformation of frozen saline soil (Sego and Ogata), frost heave of saline soil (Chamberlian, 1983), effect of salt concentration on unfrozen water (Banin and Anderson, 1974) and water and ion migration in opening system (Ershov and Ershov) in abroad. Salt expansion research has not been systemically studied. The processes of salt expansion are mainly studied for coarse grain saline soil under constant temperature at upper plate. At the same time, the effect of the sample with salt concentration layer on salt expansion is considered in this study.

In order to discuss and analyze the processes of salt expansion that affect the stability of engineering building, the salt expansion experiments of coarse grain saline soil with Na2SO4 are developed. The salt expansion of coarse grain soil with and without salt concentration layer is designed to compare their difference in laboratory. The results show that the coarse grain soil with salt concentration layer produced abrupt destroyed salt expansion if there is suitable water content. However, coarse grain saline soil without salt concentration layer was not able to produce the larger salt expansion that destroys engineering construction.