Research On Active Cooling Technology For Permafrost Foundations Of Hydraulic Structures

In recent years,China in the cold area of frozen soil scientific research progress can be described as remarkable success.Especially in the frozen soil area,railway subgrade and Sino-Russian crude oil pipeline foundation treatment as the representative of the research and development work have achieved satisfactory results.However,the permafrost region is extensive.Only China's various types of frozen soil area reached more than 75% of the land area.The vast expanse of frozen soil is rich in resources.And with the China's comprehensive national strength has been substantially increasing,the construction of frozen soil resources development projects and the number of scale are increasing,the requirements of construction technology and technical standards in different projects are different.Coupled with the global climate warming have a bad effect on the stability of the structure of frozen soil.The researches of controlling damages are more urgent and more necessary.The paper is based on the active cooling technology of permafrost foundation in Daxinganling area of Heilongjiang Province.And paper aims to explore the best effect of different heat pipes arrangement pattern to reduce the permafrost upper limit of permafrost foundation and ensure its stability.The working period,working state and working radius of the heat pipes under different environmental conditions of the permafrost foundation in the Daxing'anling area were studied by numerical simulation.The experimental data were analyzed and compared with the experimental data.In the cooling effect,it is found that the heat pipes are not working continuously for a period of about 5 months and the actual working time is about two-third of the working cycle.The cooling effect of the heat pipes foundation in winter is obvious,which is beneficial to increase of the cold storage and improve the thermal stability of the foundation.The cooling intensity of the cold rod produced by the heat pipes in the foundation decreases with the increase of distance,the effective radius is 1.9 m,and the depth direction reaches the maximum value at the heat pipe evaporation section.The results show that the spacing of 3.6 m is reasonable in the heat pipes test project of the permafrost foundation in the Daxing'anling area,The Refrigerating effect of heat pipes without covering thermal insulation board is better than that on the surface covered with insulation board.