Analysis Of Water And Salt Migration Law And Subgrade Stability Of Saline Soil Subgrade Under The Condition Of Precipitation Infiltration

As a special soil,saline soil has a wide distribution area in northwestern China.It is stipulated in relevant codes and standards.Weak saline soil and medium saline soil can be used as roadbed fillers in highway engineering construction.When conditionally using local saline soil for roadbed filling,many factors are involved,including: type of soil(coarse-grained soil,fine-grained soil),salt content,salt-bearing properties,applied layer Position,precipitation and surface water,climate and environmental conditions,etc.,the correct control of the degree of influence of these factors is the key to the rational use of saline soil,and is also the focus and difficulty often concerned in the research of road construction technology in saline soil area.At present,there are many researches on the law of water and salt migration and mechanical properties of saline soil under the action of temperature gradient,and rich research results have been achieved,but there are few reports on related research under precipitation infiltration conditions.In view of the above problems,from the perspective of precipitation infiltration,through laboratory experiments,the water and salt migration law,mechanical properties and road performance changes when saline soils with different particle sizes and different salt contents are used as roadbed fillers are studied.And the finite element numerical simulation is used to analyze the stability of the saline soil roadbed under the conditions of precipitation and infiltration after water and salt migration.(1)Chlorine-salinized low-liquid-limit silt has experienced multiple precipitation infiltrations,and the downward migration rate of the peak value of water content and salt content gradually slowed down.The water content of the entire soil column rose,and the water content increased by more than 30% in the middle.The salt gradually migrates to a depth below 30 cm,with the largest increase from 30 cm to 60 cm,and the salt below 60 cm accumulates slowly.The salt content ranges from 0.5% to 2%,and the peak moisture content and the peak salt content both lag 5 cm to 10 cm.(2)Chlorine salinity grading good gravel after 3 precipitation infiltrations affects the entire soil column.At this time,the water content is evenly distributed along the depth range at about 4%,and the salt quickly migrates and accumulates to the bottom of the soil column.(3)The shear strength and bearing ratio of silty low liquid limit silt first decrease with the increase of salt content.When the salt content exceeds the critical value,it increases with the increase of salt content.When the water content is from 9% to 12%,the critical value is from 4.5% to 6%.When the moisture content of well-graded gravel is low,the salt content exceeds a certain value,the bearing ratio increases with the increase of salt content.When the water content is high,the bearing ratio does not change significantly with the increase of salt content.(4)When subgrade filled with weak saline soil,the stability of the roadbed is better than that of the medium saline soil.During the use of the saline soil roadbed,the stability of the roadbed decreases due to the migration and accumulation of salt,but it still meets the requirements.