Research On Heating Method Of Railway Subgrade In Seasonally Frozen Area Based On Geothermal Energy Utilization

Seasonal frozen soil accounts for more than 50% of China's land area,among which there are many railway lines.At present,the measures for preventing and controlling frost heave of subgrades in seasonally frozen areas are limited to improving subgrade filling,drainage and passive insulation,which lacks effectiveness and initiative,resulting in the widespread existence of subgrade frost heaving diseases,which seriously affects train safety.Therefore,a new measure is urgently needed to effectively solve the problem of roadbed frost heaving.This article relies on the National Natural Science Foundation's project "Research on the Active Temperature Controlled Subgrade Thermal Regulation Mechanism and Heating Method for Railways in Frigid Regions",The National Natural Science Foundation of China Youth Project "Study on the seasonal variation law of active layer freezing and thawing parameters based on active and passive microwave remote sensing technology".Based on the full investigation of the geothermal energy development and utilization technology,measures were proposed to actively provide heat to the roadbed,regulate the balance of heat and expenditure of the roadbed,and resolve the roadbed frost heave.Developed "integrated artificial heating pipe".At the same time,a "ground-gas coupling model" was established to simulate the temperature field of the roadbed.The following research results have been obtained through the test and simulation analysis of the "integrated artificial heating pipe" :(1)Based on the interdisciplinary research,a design method for artificial heating pipes is proposed.According to the characteristics of the pre-application area,according to the design process and method proposed in this article,the compressor,heat dissipation section,capillary tube and heat collection section of the artificial heating tube and the selection and calculation of refrigerant are calculated.(2)Test in three modes of "integrated artificial heating pipe",it is found that the temperature of the pipe wall of the heat dissipation section shows a middle-high and two-pass low distribution characteristics under continuous and intermittent working modes.It has a good heating effect on the surrounding soil,and the heating radius can reach 2 m.The minimum temperature of the tube wall in the heat collecting section can be below-10 ?,which can effectively absorb the geothermal energy of the surrounding soil.(3)Based on the full consideration of the influence of solar radiation,wind speed,ambient temperature,geothermal and other factors on the temperature field of the roadbed,a "geo-air coupling model" was established.Compared with the method used by many scholars to simulate the temperature field of the subgrade using the "attached layer" theory,the establishment of this model does not require large-scale and longterm ground temperature monitoring of the subsection,and has stronger engineering applicability.(4)Aiming at the structural characteristics of railway subgrade,the concept of "separate artificial heating pipe" was proposed.Through the simulation analysis of the application effect of "separate artificial heating pipe" in the roadbed,it is found that compared with the "integrated artificial heating pipe",the separation type has better heating effect in the railway roadbed.At the same time,the combined measures of active heating by artificial heating pipes and passive insulation by thermal insulation boards can more effectively regulate the temperature of the roadbed.