Experimental Study On Soluble Salt Capillary Migration In Unsaturated Compacted Loess

Unsaturated compacted loess is one of the main subgrade materials in arid and semiarid regions.Because of the strong evaporation,the capillary rising of the free water in the subgrade will inevitably lead to the upward migration of the salt,and the salt will accumulate in the upper part of the soil,which can affect the engineering properties of the subgrade,and will led to a series of secondary disasters and damage the roads and ancillary facilities.This study was supported by the National Natural Science Foundation of China?No.51878322?.The loess used in the experiment was taken from Lanzhou City,Gansu Province,China.Under the indoor conditions,the improved water-salt migration device was used to study the SO₄^2-and Cl^-capillary migration characteristics of unsaturated compacted loess in different dry density,different migration fluids and different intercepting-layer.The conclusions are as follows.?1?In different dry densities,the Cl^-and SO₄^2-migration rate of the compacted loess follows the trend of 1.69g/cm³>1.5g/cm³>1.32g/cm³,and Cl^-migration rate is greater than SO₄^2-;the effect of dry density change on Cl^-migration rate is greater than that on SO₄^2-.?2?Under the different migration liquids,the ion migration rate of Na₂SO₄ and KCl mixed migration liquid in the compacted loess is greater than that in the single migration liquid.For example,the Cl^-migration rate in mixed migration liquid of the compacted loess is higher than that in KCl migration liquid;the SO₄^2-migration rate in mixed migration liquid of the compacted loess is higher than that in Na₂SO₄migration liquid.?3?The alkali-activated geopolymer intercepting-layer and the lime-fly ash intercepting-layer can effectively hinder the migration of Cl^-and SO₄^2-,and the inhibition effect on Cl^-is greater than SO₄^2-.The alkali-activated geopolymer intercepting-layer has a greater inhibitory effect on SO₄^2-than the lime-fly ash intercepting-layer,and the lime-fly ash intercepting-layer has a greater inhibitory effect on Cl^-than the alkali-activated geopolymer intercepting-layer.?4?The lime-fly ash cushion can be preferentially used in the chlorine saline soil subgrade,and the alkali-excited geopolymer cushion can be preferentially used the sulphate saline soil subgrade,which can better hinder the migration of the soluble salt in the soil.