Study Of The Cooling Effect And Mechanism Of Wind Refrigeration Embankments In Permafrost Regions

With the proposal and development of the national strategy,"Belt and Road" and economic development of the Qinghai-Tibet Plateau,the traffic load in the permafrost regions of Qinghai-Tibet Plateau will inevitably increase sharply,leading the construction of high-grades wide embankment is an inevitable trend.However,due to the strong heat absorption effect of high-graded wide embankment,Existed cooling measures can not satisfy the cooling requirements under the climate warming condition.Therefore,this paper first summarizes the main passive measures that have been applied to mitigate permafrost degradation underlying the embankments in the permafrost regions of the Qinghai-Tibet Plateau,and objectively evaluate its engineering service performances in infield monitoring,indoor and outdoor experiment,numerical simulation and structural optimization.Then,we proposed a concept of wind-cooled embankment based on the principle of cooling refrigeration systems such as air conditioning: using the rich wind resources in the permafrost regions of the Qinghai-Tibet Plateau to drive compressors to convert wind energy in permafrost regions into energy cooling the embankment,thereby alleviating the degradation of the permafrost underlying embankments.This new wind-cooled embankment has a series of advantages such as safety and environmental protection,uniform cooling and energy renewable.This paper conducts the calculation of wind blade output power,refrigeration system input power,and cooling capacity,and design indoor model test according to similar theory.Comparing the results of indoor model test and numerical simulation,the correct relevant parameters are obtained;we then conduct the numerical simulation for the long term stability of wind-cooled embankment.The theory calculation,indoor model test and numerical simulation all show that wind-cooled embankment can effectively reduce the embankment temperature in the permafrost region and thus raise the artificial upper limit of permafrost,some preliminary conclusions can be obtained:(1)Based on the required calculated parameters in published paper,we calculate the wind blade dynamics characteristics,and find that the power provided by the wind blades in the permafrost region is sufficient to drive the compressor to operate and cool the embankment;(2)Based on the calculation results,the indoor model test of asphalt concrete roadbed and cement concrete roadbed is carried out on the wind-cooled roadbed under the same boundary conditions according to the similarity theory.It is concluded that the wind-cooled roadbed can effectively reduce the temperature of frozen soil and effectively raise artificial upper limit of frozen soil,thereby keeping the frozen soil embankment be stable;(3)The frozen soil underlying the control indoor embankment without any cooling measures shows an obvious degradation;the degradation rate of frozen soil underlying asphalt concrete embankment is higher than that underlying concrete embankment;(4)Comparing the results of numerical simulation and laboratory experiment,it is found that the numerical results is basically same to experimental results,validating the rationality of the numerical simulation;and the partial differences is because the simulation simplifies the heat transfer of the roadbed and can completely shield the external environment from the simulation(5)Based on the solid heat transfer equation,considering the temperature rise of 2.6 °C in the next 50 years and ignoring the moisture migration,the long-term stability of the wind-cooled embankment is numerically studied using COMSOL;it is found that wind-cooling system has relatively good cooling effect when applied in high-graded wide embankment,and can effectively maintain the stability of permafrost underlying embankment during the service life.