Analysis Of Subgrade Soil Properties And Microstructure Under The Action Of Freeze-thaw Cycle In Season Frozen Zone

The road generally will be affected by the influence of the freeze-thaw action and produce disease because of the influence of the special climate in season frozen zone.But the subgrade disease research has not caused enough attention of domestic researchers.In order to find out the strength properties of the subgrade soil changes under the action of freeze-thaw season frozen area,the research chose three representative level highway in heilongjiang province,then surveyed the subgrade moisture content and the changes with the seasons before and after the winter and judged dry and wet conditions of the subgrade.In order to research the change rules of the subgrade strength under freezing and thawing cycle, the article get sample soil and did strength test under different conditions in the laboratory and scanning electron microscopy are used to study the micro change mechanism of subgrade soil after freezing and thawingThe survey found that the subgrade soil moisture content after the spring melting was higher than before the winter freeze and most surveyed highway subgrade were in the damp or wet state.Laboratory test showed that the modulus of resilience of soil decreased with the decrease of degree of compaction and increased with the decrease of the moisture content and the lower the degree of compaction, the greater the influence coefficient of moisture content of the soil modulus of resilience when freezing and thawing cycles at the same time.The study also found that The freeze-thaw action can reduce the modulus of resilience of soil and the freeze-thaw cycle, the more the greater the attenuation value of modulus of resilience and after6times freezing and thawing, the modulus decrease stable basically.The freeze-thaw cycle action can also reduce the cohesion of soil, increase the internal friction angle and the cohesion of the silty clay affected by freeze-thaw action was largest.With the increase of degree of compaction, all kinds of soil cohesion and internal friction Angle values have varying degrees of increase and Sandy soil cohesion change was the most obvious.With the increase of moisture content, soil cohesion and internal friction angle will be lower,and silty clay cohesion and internal friction angle is affected by the moisture content mostly.Scanning electron microscopy found that The internal structure of soil will change after freeze-thaw cycle and the pore Between the particles develop and the contact between particles become more loose.These changes will cause a decline in the mechanical properties of soil.