Thermal And Mechanical Behavior Of Highway Thermosyphon Subgrade In High Latitude The Patchy Permafrost Regions Of Northeast China

Two-phase closed thermosyphons(TCPTs)are widely used in cold region engineering maintenance,and has been used in many countries and regions.The North line of the Belt and Road Initiative throughs a large,high latitude patchy permafrost pegions.As China and the Arctic Circle countries are more and more closely related to Russia and Finland,the settlement of roadbed diseases in high latitude permafrost regions will be conducive to the traffic interchange between the northern route countries and the cooperation between various countries.At present,the highway engineering and pipeline engineering in Northeast China have gradually introduced two-phase closed thermosyphons,but the relevant theoretical research and applied research on the application of thermosyphons in Northeast China are relatively less.In order to further improve and enrich the thermosyphon theory,and provide guidance and reference for the use of the thermosyphon in the Patchy Permafrost Regions of Northeast China.In this paper,based on the investigation of highway subgrade diseases in Patchy Permafrost Regions of Northeast China and the analysis of relevant data of existing thermosyphon projects,a three-dimensional thermosyphon subgrade model is established by using finite element analysis method,and the model is verified.Based on the theoretical model,the evolution law of thermosyphon subgrade and the working state of thermosyphon are studied.The purpose of this paper is to provide a theoretical reference for the application of thermosyphon in Patchy Permafrost Regions of Northeast China.On this basis,the finite element method is used to study the thermodynamical behavior of thermosyphon subgrade under traffic load.Specific research contents and achievements include:(1)Based on COMSOL software,the numerical model of subgrade in the Patchy Permafrost Regions of Northeast China is established by using finite element method.Considering the influence of thermosyphon in the temperature field of permafrost subgrade,the thermosyphon-permafrost subgrade model is established.According to the existing highway design data and field temperature monitoring data,the numerical model parameters and boundary conditions of highway thermosyphon subgrade in permafrost region are determined,and some road diseases and treatment schemes in Daxing’an Mountains and the Xiaoxing’an Mountains are analyzed,The climate and geological differences along the Jiatang highway and Chaimu railway across the Xiaoxing’an Mountains.(2)The influence of the shape of condensation section,heat dissipation area,wind speed,air temperature and frozen soil environment on the heat transfer power is considered.Based on the simulation calculation of the thermosyphon-permafrost subgrade in Zhangling area,the working state of thermosyphon and the temperature evolution law of the thermosyphon subgrade are analyzed,and the cooling effect of the thermosyphon put into use at different times on the subgrade is discussed.The working state and performance of thermosyphon in the Northeast the Patchy Permafrost Regions of Northeast China were studied,including the working time period and effective cooling radius.This paper studies the influence of different transverse arrangement,insertion depth and shape of thermosyphons on the temperature field of existing permafrost highway subgrade.Based on the climate difference between Qinghai Tibet region and Northeast China,the difference of using effect of thermosyphon is analyzed.(3)This paper studies the dynamic response of Subgrade under traffic load under the optimal arrangement of thermosyphons,analyzes the distribution of dynamic body stress and dynamic deviator stress of Subgrade under traffic load,different speeds and different axle load conditions,and the stress path of soil element under traffic load.