Study On The Laws Of Capillary Water Migration In Unsaturated Compacted Loess

With the implementation of the West Development Strategy and the"Belt and Road"construction,the construction of highway and railroad are enlarged and lots of unsaturated soil are gradually used as subgrade materials.However,the change of time and space distribution of water lead to the occurrences of post-construction settlement,strength reduction and frost boiling of compacted loess subgrade.Therefore,it is of great significance to analysis the law of capillary water migration in subgrade soil for road construction in Northwest China.The laboratory test in simulating capillary water rise was constructed to analyze the law of water content and electrical conductivity of the compacted loess column at different migration solution,compactness and isolated layer in this paper which was funded under the NNSF of China（NO.51878322）.The main conclusions are shown as follows:（1）The water contents of the compacted loess columns in four kinds of migration solution accord to the distribution of capillary rise,and decrease linearly with the increase of height.At the same time,the water capillary migration ability of the soil columns in different kinds of migration solution decreases in the order of mixed KCl and Na₂SO₄ solution>Na₂SO₄ solution>KCl solution>distilled water.The electrical conductivity decreases in the order of mixed KCl and Na₂SO₄ solution>KCl solution>Na₂SO₄ solution>distilled water.The salt migration rate is slower than the water migration rate and the salt transport capacity decreases with height.（2）In the soil columns with different compactnesses,the distribution of capillary water is uneven in rising range.Capillary water rise is affected by size of pores.The rising height and rate of capillary water increase with the increase of compactness.The conductivity distribution of each layer at different compactnesses was random in the early stage of the trial and increased with the increase of compactness from the 5th day.（3）For the compacted soil columns with lime-fly ash solidified loess isolated layer,the water content decreases with height,but the conductivities at different heights are not different.For the compacted so il column with the solidification layer of loess solidified with an alkali-activated geopolymer,the water content increases firstly and then decreases with the height.The peak of the water content appears at the height of 40 cm,but the conductivity alternates between rising and falling at this height.The water content and conductivity of the overlying soil of the two soil columns with solidified loess isolated layer are clearly below the one without isolated layer in this range.With the solidified loess isolated layer settled,the height and velocity of the capillary water and the ions are effectively slowed down,which is beneficial to the overall stability of the unsaturated compacted loess.