The Analysis Of The Cooling Roadbed's Cooling Effection In Cold Regions

With the national polices'implementation of the western region development and the northeast old industrial base promotion ,the large-scale infrastructure will arrive a new peak-period in the next decades years.So,traffic construction,as the No.1 task of economic development,will be accelerated in the mountainous northeast and northwest region in China.Out of question,more and more roads in the higher elevations of the Tibetan Plateau will be built in these cold region in China.But at present,the roadbeds in cold regions built in the cold and high altitude regions have encountered many kinds of disasters differently.From the damaged styles of the roadbed in the cold regions have appeared now,the damaged styles of these roadbeds are mostly the frost-heave and the thawing.Therefore,effective measures and appropriate must be applied to reduce the influence of embankment and preserve underlying permafrost so that the embankment can keep stability in permafrost regions,which have been the research objective for permafrost engineers and scientists.Many experts and scholars at home and abroad propse sevral frozen soil protection measures applied in the engineering practice at present,such as louvres.ventilated tubes embankment.air cooled embankment.thermal pipe and the embankment with insulation layer and so on.Although they have some effections in resolving road diseases in cold regions ,they are also disadvantage.With warming of the global temperature,they will face great challenge. As a new kind of embankment structure,the cooling roadbed plays an important role in protecting the permafrost actively.It balances the thermal between the permafrost and the outside of the embankment by the heat exchange of the water in several closed water tank buried in the roadbed,and protects the frozen soil.The water tank formes the structural layer with adjusting the heat balance in the roadbed,and saves the energy by the endothermic and exothermic during the phase change of the heat exchange so that it can effectively inhibitions the subgrade diseases such as the frost-heave and the thawing in the permafrost.It's construction cost and the using costs are lower than the thermal pipe's,and the cooling effection are better than the other measures,so it is applied widely in any embankment of the cold regions.The article will analyze the cooling effection of the cooling roadbed from its temperature features and the nodes'annual temperature changing over time under the basal and the temperature of the subgrade midline changing with the depth in different times.At the beginning,influencing factors of permafrost regime are analyzed according to climatic conditions,intrinsic factors in permafrost and characteristics of highway structure.Some advanced technologies of embankment construction in permafrost regions are also introduced.And then,on the themal conduction differential equation,the finite element model(FEM) of the temperature field with phase change about general embankment is founded using enthalpy field,and the calculation of the parameters in the finite element formulations are detailed derivation.Finally, the temperatures of the ordinary embankment and the cooling roadbed in the cold regions are analysed by the finite element software ANSYS,and there is a conclusion that the cooling roadbed in the cold regions lifts the upper limit of permafrost.The structure layer of the water tank plays a dual role by inhibiting the downward transport of the cold in cold seasons and shielding the heat in warm.The cooling roadbed plays a positive and effective role in protecting the frozen soil.and also it provides sugestions about the construction of the embankment in the cold regions under the trend of global warming.This will provide a theoretical basis and reference on the constructions of the embankment in cold regions.