Experimental study on salt expansion and thawing subsidence properties of sandy saline soil

In Northwest China, there is a large amout of sandy sulphate and sulfite saline soil. This saline soil can be used as embankment fill, which can make full use of local resources and save construction cost of highways. Taking the subgrade filling standards and reasonable drainage facilities as the prerequisite conditions, based on the soluble salt content preparation method of screening method of 5 mm, the salt expansion change characteristics of sandy saline soil from the single cooling tests and the thawing subsidence characteristics of sandy saline soil from the experiments on freeze-thaw cycles are studied under different salinity levels. It is shown that the inception temperature and sensitive temperature range of the sandy sulfite saline soil are 5℃ lower than those of the sandy sulphate saline soil. When the salt content is less than 1%, the salt expansion rate of sandy sulphate saline soil is less than 1.5%. When the salt content is less than 2.3%~2.5%, the salt expansion rate of sandy sulfite saline soil is less than 1.0%. Under several freez-thaw cycles, the sandy sulfite saline soil has strong thawing subsidence characteristics. Under the conditions of allowable deformation of pavement being 2 cm and embankment thickness 2.0 m, the limit of sandy sulphate saline soil is 1.0% and the limit of sandy sulfite saline soil is 2.3% for subgrade fill.