Study On Water Salinity Migration And Mechanical Properties Of Weak Saline Soil

Saline soil is a special soil,which has different properties from ordinary soil.When is used as subgrade filling,we needs to consider various factors that affect the stability of the subgrade.The change of water,salt and temperature in soil will have an effect on soil structure,and change the subgrade mechanical performance.This will cause uneven settlement,cracks and other disease in road.In order to explore water and salt migration and mechanical properties of saline soil under different conditions,it did the indoor test of water and salt migration in supplying water condition and the freeze-thaw cycle condition,and did unconfined compressive strength test and bearing plate test.It analyzed the mechanical properties influence of the freeze-thaw cycle to weak saline soil.The main conclusions are as follows:(1)Analyzed the applicable conditions and advantages and disadvantages of the existing test methods of water content and salt content;A method for determining the salt content of soil by ECH2 O was proposed,and the relation formula between conductivity and salt content was established.(2)The effect of water content and salt content on water and salt migration was analyzed through the experimental study under supplying water condition.Test results show that both water and salt present a tendency to migrate from the bottom up The water migratiaton is mainly caused by the joint action of gravity potential,matric potential and solute potential,and salt migration is largely driven by a combination of solute convection and molecular diffusion(3)In order to study the effect of freeze-thaw cycle on water and salt migration of saline soil,the soil column freeze-thaw cycle test was carried out with the best water content and salt content in 2%.The study shows that the freeze-thaw cycle can help the formation of water and salt migration channels and promote the migration of water and salt.(4)It tested the unconfined compressive resilient modulus of the small specimen under the condition of freeze-thaw cycle of saline soil with different salt content.The results show that the higher the initial salt content,the greater the deformation under the same load.After three freeze-thaw cycles,its deformation increased dramatically.And with the increase of the number of freeze-thaw cycles,the deformation amount is almost no increase.(5)Based on the test of resilient modulus of the indoor soil column and the unconfined compressive resilient modulus of the small specimen,it established the relationship between the resilient modulus of subgrade and the unconfined resilient modulus.(6)It studied and analyzed the variation characteristics of resilient modulus of subgrade in saline soil.The results show that resilient modulus of the salt soil subgrade under the freeze-thaw cycle will have three phases: decrease rapidly,decrease slowly and stabilize.The higher the initial salt content,the greater the attenuation degree of resilient modulus,the maximum can reach about 60%.The lower the initial salt content,the lower the attenuation degree of resilient modulus,and the minimum is about 25%.