| Faced with the deep changes of international economic cooperation and competition pattern,conforming to the stringent need of improving the quality of domestic economy,increasing it’s efficiency and updating it,China actively promotes the establishment of a comprehensive transportation channel that traverses the east and the west,stretches from the north to the south and makes the traffic smooth both in inland and coastal regions of China.The cold region tunnel engineerings under construction and being proposed have been increasing.However,in terms of the present status of cold region tunnel engineerings in China,the difficulty of tunnel frost damage has not been broken and there are still lots of leakage and frost damage phenomena.Based on the technology research and development subject "The key technology of cold-proof and dewatering design in high-speed train tunnels of cold regions" put forward by China Railway Corporation,applying methods such as theoretical study, numerical simulation,field test and mathematical statistics in a comprehensive way,this thesis has built a three-dimensional numerical calculation model of fluid-thermal-solid interaction around "air-lining-surrounding rock" in cold region tunnels and mainly explored the influence of meteorological elements to the temperature field of tunnels in cold regions.Major achievements and conclusions are as follows:1) On the basis of surveying relevant literature, aiming at the strong coupling relations between multi-physics in the engineering of tunnels in cold regions, this paper has drawn up the multi-field coupling diagram of cold region tunnels with several fundamental fields like air, groundwater, surrounding rock and the water flow field in waterproof and drainage facilities as the framework;2) By arranging and analyzing the measured data of Wafangdian Tunnel,the function in which the temperature outside of the tunnel changes over time,the temperature distribution law inside the tunnels as well as the follow-up relation between inside temperature and outside temperature are obtained.And combining the features of surrounding environment of the tunnel site,this paper has analyzed the relation between the wind speed and the wind frequency of Wafangdian Tunnel portal and these of Lingyuan area.It turns out that the landform has an important impact on the formation of microclimate in mountain areas;3) Taking the field experimental data as boundary conditions, a numerical calculation model of fluid-thermal-solid interaction around Wafangdian Tunnel "air-lining-surrounding rock" has been established and the reliability of this model has been verified by comparing calculated values and measured values.4) Through analyzing the basic features of meteorological factors and the influencing mechanism of them to temperature fields of tunnels in cold regions in theory,this thesis proposes to combine various meteorological factors with specific conditions of tunnels and introduce the concept of equivalent natural wind speed while abstracting the aggregative indicator of meteorological factors containing tunnel portal temperature and equivalent natural wind speed,which are both used in solving the temperature field in tunnels of cold regions.5) According to different dominant factors for the formulation of natural airflow,the paper suggests that tunnels in cold regions can be divided into wind-dominated tunnel, thermal head dominated tunnel, wind and thermal head dominated runnel, and air pressure gradient affected tunnel.In addition,it advised to differentiate these tunnels during the cold-proof design of tunnels.Through the numerical simulation,the effect law of the average temperature in the coldest month,the winter prevailing wind direction and wind speed to the temperature field of wind-dominated tunnels has been veiled.Finally,based on the numerical simulation of multiple load cases,this thesis has obtained the regression function between the length of longitudinal influence and the tunnel portal temperature as well as the equivalent natural wind speed.It turns out that the impacts of the tunnel portal temperature and the equivalent natural wind speed to the temperature field of tunnels in cold regions are mutually reinforced.6) The thesis has initially put forward the principles and corresponding standards of longitudinal cold-proof zones of tunnels in cold regions.Considering the positions where the average temperature in the coldest month is 3 degrees below zero and the average temperature in the coldest day is 0 degree within the tunnel as the critical value of partition standardization,the paper longitudinally divides the tunnel into strong influence zone,weak influence zone and influence-free zone and has analyzed a specific case at the same time. |
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