Research On Anti-freeze Technology Of High-altitude And Cold Region Highway Tunnel

With the development of China's infrastructure construction,there will be many large tunnel projects in high-altitude areas in the future.However,the construction of tunnel in high altitude and cold region will inevitably face the problem of anti-freeze in tunnel.It can be seen from the domestic and overseas engineering examples that the freezing damage has an unnegligible impact on the tunnel,so it is very urgent to study the anti-freeze of the tunnel in high altitude and cold region.This paper is based on the practical project of Xueshanliang tunnel in Aba,Sichuan Province.Firstly,the project environment temperature was investigated as the basis of research.After consulting a large number of relevant literature,by using the method of numerical simulation established tunnel model of different insulation layer setting method,different thermal insulation materials and different insulation thickness,finally has made the further optimization of the mode of drain heat preservation.The main conclusions in the study are as follows:(1)The thermal insulation layer can effectively reduce the influence of low temperature on surrounding rock,and the low temperature area in surrounding rock decreases significantly.Moreover,when the insulation layer is set on the secondary lining surface,the insulation effect is better.(2)In the calculation of polyurethane,polystyrene,and rock wool insulation materials,polyurethane has the best thermal insulation effect,and the polystyrene foam secondary,the rock wool insulation effect is the worst.And the thermal insulation effect is better than that of ordinary concrete when the slag bead concrete is used as lining concrete.It is suggested that polyurethane + expanded slag bead concrete should be used in the tunnel entrance of cold area under the premise of satisfying structural bearing capacity.(3)When the polyurethane foam board is used as thermal insulation material,the temperature difference between the two sides of the thermal insulation layer increases by 0.4 to 0.9 degrees Celsius for every 1cm increase in the thickness of the thermal insulation layer.With the increase of the thickness of the insulation layer,the increase of the temperature difference between the two sides of the insulation layer becomes smaller.(4)The length of the insulation section calculated by the Kawasaki's formula is about 639.93 m.The insulation length of the Partridge Mountain Tunnel in the same area is about 800 m.The openings at both ends of the main tunnel used in the Xueshanliang Tunnel are about 720 m.Insulation fortification length can basically meet the requirements of the tunnel insulation.(5)In the original design depth of 1m,can not meet the requirements of the central drain antifreeze.It is suggested that the depth of the central gutter at the entrance should be increased to 1.5m.If it is impossible to increase the embedment depth of the central drainage ditch,a thermal insulation layer may be provided inside the cover of the drainage ditch and on both side walls of the drainage ditch to enhance the antifreeze resistance of the drainage ditch and ensure that the groundwater in the drainage ditch will not freeze and form a frost heave image Structural safety.