The Three-Dimensional Analysis Of The Temperature Field Of Long Tunnel In Cold Regions And Study Of Heat Preservation

In order to calculate and analyze the temperature ifeld changes of the tunnel lining andthe surrounding rock when piston wind through the cold regin tunnels, verify the necessityand rationality of the insulation layer designd in the tunnel lining of cold regions, anddetermine the effectiveness and economic of the insulation design，in this paper, the KunlunMountain Tunnel of Qinghai-Tibet railway was studied, combined with the thermodynamicproperties and the unique characteristics of Kunlun Mountain, using CFX in ifnite analysisprogram ANSYS Workbench software modules, create the three-dimensional ifnite elementanalysis model including the surrounding rock，the tunnel lining and the air inside the tunnel,iftted the temperature of entrance of the Kunlun Mountains tunnel into a sine curve,considering factors such as the phase change of permafrost, the actual engineering of KunlunMountain Tunnel is analyzed. First analysis of the Kunlun Mountain Tunnel without thermalinsulation after it penetration, the piston wind influence on tunnel arch lining concrete surface,and the distribution of temperature ifeld in the surrounding rock of the tunnel. Then add5cmthickness of polyurethane insulation board into the three-dimensional ifnite element analysismodel according to the practice engineering to verify the actual effect of the insulation layerlayed in lining of the Kunlun Mountain Tunnel. Finally, make study of heat preservation ofcold region tunnels.This paper mainly studies the following aspects of content:First of all, made a detailed introduction of tunnel aerodynamics and the thermalenvironment of cold region tunnels in the domestic and international research anddevelopment, and also made introduction of the basic of heat transfer, including thetemperature ifeld and its classiifcation, convective heat transfer differential equation of heatconduction, the heat balance equation, boundary conditions, and heat conduction problemsassociated with the phase change;Second，create a three-dimensional ifnite element analysis model including thesurrounding rock，the tunnel lining and the air inside the tunnel, consider the temperature ofthe Kunlun mountain tunnel entrance and the velocity of piston wind, use the sensible heatcapacity method to deal with the phase change, and add all feature parameters of thepermafrost to the model，slove the influence of the piston wind to the temperature ifeld of theKunlun Mountain Tunnel without the insulation layer in the tunnel lining，including thetemperature-time curve on the cross-sectional of the tunnel depth of5m，50m，100m，150m，200m，250m，298m，the temperature amplitude of the tunnel arch lining surface andsurrounding rock of the tunnel, the depth that the temperature could relay and the scope ofsurrounding rock seasonal freezing and thawing; Thirdly，add5cm thickness of polyurethane insulation board into the three-dimensionalifnite element analysis model according to the practice engineering，slove the inlfuence of thepiston wind to the temperature ifeld of the Kunlun Mountain Tunnel when it has insulationlayer in the tunnel lining，including the temperature-time curve on the cross-sectional of thetunnel depth of5m，50m，100m，150m，192m，the temperature amplitude of the tunnel archlining surface and surrounding rock of the tunnel, the depth that the temperature could relayand the scope of surrounding rock seasonal freezing and thawing, verify the reasonableness ofthe insulation layer that designed in the Kunlun Mountain Tunnel, simultaneously, makeanalysis of the two differencedate in the two cases, which could provide a reference for thesimilar engineering and design of thermal insulation;Fourth, the article lists eight domestic tunnels which have been completed in coldregions, for their project summary and insulation measures are summarized. Then thermalinsulation about the cold region tunnels are studied from two aspects of anti-freezing andfreeze protection. Wherein the anti-freezing measures include the use of antifreeze concrete,reinforced concrete, increasing the thickness of the lining and other measures; the freezeprotection measures include insulation method (the thermal insulation layer are put at theinner surface of the lining，or put between the lining and the surrounding rock，or put awayfrom the lining，with the air between them), waterproof and drainage method (insulation ditch,center deep ditch and warm drainage tunnel), cold-proof door method, air curtain method,sunshine shed meathod, heating measures(the U-shaped heating tube setted at the back of thelining，dual-source heating method at the back of the lining of construction joints, heatingthrough the tunnel and gutter heating measures), grouting reinforcing measures and so on.Finally, select a freezing measure-air curtain, slove the inlfuence of the piston wind tothe temperature ifeld of the Kunlun Mountain Tunnel when air curtain’s spray angle is0°, andat the same time, ejection speed is Sm/s, including the temperature-time curve on thecross-sectional of the tunnel depth of5m，50m，100m，150m，200m，234m，the temperatureamplitude of the tunnel arch lining surface and surrounding rock of the tunnel, the depth thatthe temperature could relay and the scope of surrounding rock seasonal freezing and thawing.The results show that the surrounding rock still will eventuate seasonal freezing and thawingcycles from tunnel entrance to a certain range so that the tunnel lining structure destroyedwhen the air curtain is used.