Study On The Treatment Technique Of Uneven Deformation In The Permafrost Subgrade

The Qinghai-Tibet Highway is located in the hinterland of the Qinghai-Tibet Plateau,which passes through550km permafrost region from north to south. Because of the specialengineering and harsh climate, the uneven deformation of the sugrade appeared seriously inpermafrost region. This paper studied on the forming of the uneven deformation and thetreatment technique with the research methods of field investigation, numerical modeling andtest road construction.The Qinghai-Tibet highway site investigation shows that the longitudinal cracks,subgrade uneven deformation (lateral uneven deformation and longitudinal wavedeformation), subgrade subsidence, loose slope are the main types of subgrade diseases,pavement crack, rutting, pits and unheaval are the main types of pavement diseases. Subgradeuneven deformation is composed of filling subgrrade deformation, the seasonal active layerdeformation and the permafrost melting deformation.This paper established the unsteady temperature field control equation with phase transition,the moisture migration control equation and stress and deformation control equation ofpermafrost subgrade. This paper simulated the subgrade temperature field of the typicaltransverse section in Wudaoliang areas. The subgrade temperature field distributioncharacteristics was analyzed after the road completion of1year,5years,10years,15yearsand20years.Based on the elastic-plastic theory of the soil deformation, the control equation of thepermafrost subgrade stress field and deformation field was established. This paper putforward calculation flow to solve the subgrade stress field and the deformation field with theapplication of the finite difference software FLAC3D. Considering the subgrade temperaturefield impact on the subgrade deformation, the basic model of permafrost subgrade transverseuneven deformation with the effect of shady slope and sunny slope was established. Thispaper calculated the change characteristics of subgrade transverse uneven deformation underthe condition of different subgrade heights, different permafrost upper limits and residualthawed layers. Considering the roadside hydrops impact on the subgrade longitudinal unevendeformation, the permafrost subgrade longitudinal uneven deformation model was established.The test site was the section from k3035+980to k3036+000of Qinghai-Tibet highway,which was used the CGMT with the slope seepage measures to treat the uneven deformation.The construction process and construction technology was introduced based on the test site.This paper investigated road condition and evaluated the reinforcement effect of treatmenttechnique.