Abstract: Research about salt and frost heaving is helpful to further know the engineering properties of sulfate (sulfurous) saline soil. In order to find the characteristics of salt and frost heaving, the authors introduce the results of the tests of singlecycle salt and frost heaving for the sulfate (sulfurous) saline soil on fine soil plain of Shuimohe Valley in north Tianshan.The test results show that: (1) The singlecycle salt and frost heaving rate increases with the decrease of temperature, and the soil expansion is mainly salt heaving before soil frozen but saltfrost heaving after frozen. The saltfrost heaving tends to stable when below -15℃. (2) The inception temperature of heaving decreases with increase of water content in the same sulfate content, and it depends on sodium sulfate crystallization temperature, sodium sulfate crystal content, soil microstructure, internal frictional resistance, cohesion, attraction among soil particles and extent of adsorption of sodium sulfate in void. (3) The singlecycle salt and frost heaving rate interval increases with increase of sulfate content.

Key words: sulfate (sulfurous) saline soil, salt heaving, frost heaving