| Ventilation pipe subgrade is a kind of active engineering measure which is widely used at home and abroad and is very effective in protecting permafrost.However,it is mainly applied in highway and railway subgrade in permafrost area,and there is no precedent for its application in airport runway subgrade at present.In addition,there is almost no research on the application of ventilation pipe subgrade in airport runway in permafrost area at home and abroad.According to the 13 th five-year plan of CAAC,airport construction will be carried out in permafrost areas in the future.However,the permafrost is very unstable and sensitive to temperature changes,which is a major difficulty in the construction of airport runways in permafrost regions.Moreover,the construction of a runway on the permafrost is bound to cause disturbance to the heat exchange conditions of the permafrost,causing the temperature of the permafrost below the runway to rise and the bearing capacity to decline,and even affecting the normal use of the runway.Therefore,the research on runway temperature control measures in permafrost area is extremely urgent.Therefore,this paper studied the feasibility of applying ventilation pipe subgrade to airport runway in permafrost area through FLUENT,a numerical simulation software.The main research contents and results are as follows:1.This paper summarizes the distribution characteristics,formation reasons and various factors affecting the stability of the permafrost in the high latitude of northeast China,and summarizes various problems that need to be faced in the construction of the airport in the permafrost area.Based on the engineering properties of runway and the action mechanism of various temperature control measures in permafrost area,an active temperature control measure for airport runway in permafrost area is proposed,which combines three temperature control measures,namely thermal insulation layer,gravel layer and ventilation pipe,namely through-wall ventilation pipe runway.2.According to the climatic conditions and soil properties of the permafrost region in northeast China and the basic assumptions made for the simplified model,the finite element calculation model of the through-wall ventilation pipe runway was established.The core parameters that influence the cooling effect,such as the perforation rate,depth,diameter,spacing,wind speed and ventilation time,were deduced and verified repeatedly,and the value of each parameter was finally determined when the best cooling effect was achieved.3.Established through wall ducts runway model containing wind resistance and studied the variation of the runway temperature field by the factors such as the position of wind resistance and the air permeability area,and the best cooling effect was obtained when the wind resistance was located in the middle of the ventilation pipe and the air permeability area was 30%.The cooling effect of the ventilation pipe with and without air resistance was compared,and it was finally determined that the cooling effect of the ventilation pipe with air resistance was better than that of the ventilation pipe without air resistance.4.The through wall ventilation pipe runway in the process of long running beneath the frozen soil month by month and year after year to study the change rule,and every five years to extract the runway,comparing the ground temperature of permafrost below found through wall ventilation pipe runway really has very good cooling effect5.Through the comparison between the indoor scale test and the finite element calculation model of the ventilated duct runway,the correctness of the calculation results of the model is verified,and the model is proved to have certain reference value for the practical engineering application. |
PDF Full Text Request