Water-salt migration rules in chlorine saline soil under precipitation infiltration

To explore the salt loss of chlorine salt soil caused by precipitation infiltration, the artificially configured coarse-grained soils and fine-grained soils with different salt (sodium chloride) contents were taken as the research objects, nearly 500 groups of test data were obtained under 14 conditions by the self-designed simulation test device for laboratory precipitation infiltration, and the effects of water infiltration times, soil particle size, and salt content on the water-salt migration characteristics of soil samples were compared and analyzed. The relationship between salt migration and water migration under the action of precipitation infiltration was established, the depth of infiltration effect was determined, and the distribution characteristics of water and salt in the soil column after precipitation infiltration were revealed. Research results show that for fine-grained saline soil, with the increase in precipitation infiltration times (1-4), the peak points of moisture content and salt content move significantly downward, and the salt will gradually accumulate to the middle and bottom of the soil column. As for coarse-grained saline soil, the moisture content is relatively uniform within the height range of the soil column after the second precipitation infiltration, and the continuous increase of precipitation infiltration times does not change this uniformity, while the salt will quickly accumulate to the bottom of the soil column with the moisture. The "salt along with water" relationship of chlorine saline soil is related to its easy dissolution in water, so the subgrade filled with chlorine saline soil should strengthen waterproof measures, especially coarse-grained soil filler. Although coarse-grained soil has better compactability than fine-grained soil, it is strong of collapsibility after soaking water, and the disease is even more serious. The increase in salt content within a certain range does not change the overall law of water-salt migration in fine-grained or coarse-grained soil but will reduce the migration rates of water and salt. Compared with the fine-grained soil with low salt content, the depths of peak points of water and salt of fine-grained soil with higher salt content will lag behind 5-10 cm. Under the same condition of precipitation infiltration, the relative increment in salt migration of fine-grained soil is different for different salt contents, but the absolute increment is basically the same, indicating that the salt carried by water in fine-grained soils with different salt contents is certain. © 2023 Chang'an University. All rights reserved.