Study On Highway Subgrade Stabilization And Predication Technique In Plateau Permafrost Region

In order to study on treatment measures of frozen soil distresses of Qinghai-Tibet highway, field experiments on road sections with thermal insulation slab subgrade, broken stone subgrade and non-power heat pipe subgrade in practical treatment of frozen soil distresses were made on the basis of systematical analysis of distresses of Qinghai-Tibet highway and their mechanism and relying on treatment engineering of frost soil distresses in Qinghai-Tibet highway from 2002 to 2004. Based on them, distribution laws of subgrade temperature field under fluctuant boundary temperature cycle conditions are analyzed, and different ratios of slope for general subgrade and different status when there are or not banquettes are compared by laboratory simulation and numerical analysis; thermal insulation and cooling effect of thermal insulation slab, broken stone and non-power heat pipes is respectively investigated under the trend of elevated temperature by numerical analysis, laws of subgrade deformation are predicted under the trend of elevated temperature and influences of subgrade thaw settlement on pavement stress are studies by numerical computation for observation data of representative road sections selected. A model of permafrost subgrade temperature field for asphalt pavement is established under climatic change conditions, mathematical expressions about the relation between reasonable height of subgrade and time are put forward. At the same time computation expressions of the thickness of heat insulation course and of equivalent subgrade height are proposed. The best range of particle size, the reasonable course thickness and installation position of broken stone are advised, effective operating radius is simulated and validated and the relation between subgrade thaw settlement and height of subgrade fill controlled by tension stress of the bottom of pavement layer is discussed. Researches indicate that: under double acting of climate and engineering, subgrade distresses resulting from permafrost warming under subgrade is a long-term developing process so taking engineering treatment measures can alleviate distresses development and effectively control the scale but thaw settlement of permafrost subgrade cannot be radically solved; reasonable subgrade height preserving permafrost table varies with time; reducing angle of subgrade slope and heat insulation berm can contribute little to the improvement; the insulating courses of EPS slabs are suitable for low-temperature regions; broken stone subgrade is economical and rational subgrade structure; non-power probe subgrade which can cool ground temperature is a kind of effective measure to subgrade distresses in high-temperature permafrost regions; tension stress of the bottom of pavement layer is sensitive to subgrade thaw settlement and the biggest subgrade height of subgrade should be considered to be controlled in high-temperature permafrost regions.