Effect Of Particle Size On Salt Swelling Of Sulfate Saline Soil

Sulfate saline soil is widely distributed and often associated with engineering problems,but many railways,highways,civil buildings,and wind power projects must pass through or be built in areas with sulfate soil.Therefore,it’s essential to explore the properties of this soil type and the external environmental conditions that contribute to salt swelling diseases.Currently,research on salt swelling of sulfate saline soil mainly focuses on factors such as salt type,salt content,water content,and overlying load,with less attention paid to soil particles themselves.In this paper,five kinds of sulfate saline soils with different gradations and four kinds of single particle sizes with different salt contents were artificially prepared,and the effects of particle size and gradation on salt expansion of sulfate saline soils were studied by salt expansion test under single cooling condition and freeze-thaw cycle salt expansion test.Then,the microstructure characteristics of single particle size samples after salt expansion were observed by scanning electron microscope,and the salt expansion characteristics of different particle sizes were analyzed.Summed up the following conclusions:(1)The single cooling salt expansion test of sulfate-soaked soil with different gradation shows that the gradation has great influence on the salt expansion of sulfate-soaked soil.When the salt content is constant,the smaller the silt-sand ratio of soil samples,the smaller the salt swelling,and the more obvious the sudden change of salt swelling at-5℃.With the increase of salt content,the swelling temperature of sulfate saline soil increases;The salt expansion does not always increase with the increase of salt content,but there is a critical value.Too high salt content level will have a certain inhibitory effect on salt expansion.(2)The salt swelling test of sulfate saline soil with different gradation shows that when the salt content is constant,the final salt swelling of sulfate saline soil increases with the increase of silt ratio.However,the proportion of salt swelling produced during freeze-thaw cycle decreases.When the salt content is greater than 3%,the salt expansion tends to be stable after one freeze-thaw cycle;When the salt content is less than 3%,the cumulative salt swelling increases with the increase of freeze-thaw cycles,and the cumulative growth increases with the increase of silt ratio.(3)The salt expansion test of single particle size sulfate-soaked soil shows that the overall salt expansion is low,and the salt expansion process is insensitive to temperature changes.With the increase of particle size,the final salt expansion under single cooling and freeze-thaw cycle decreases.When the particle size is less than0.5mm,with the increase of salt content,the salt swelling first increases,then tends to be stable,or even decreases;When the particle size is greater than 0.5mm,the salt swelling increases nonlinearly with the increase of salt content.