Study On Heat Transfer Through Surrounding Rock And Central Deep Buried Ditch Setting In Cold Regional Railway Tunnel

Due to lack of the cold regional tunnel surrounding temperature with variation of temperature distribution of knowledge, or underestimate the adverse effects of freezing and thawing in season frozen area, but also lack of a reasonable protection and drainage technology. It makes different extent of frost damage in a large number of cold regional tunnels, a direct threat to the stability of the tunnel structure and traffic safety and huge economic losses. The numerical simulation prediction and field test inversion analysis are the key steps to reveal the spatial and temporal distribution of temperature field in tunnel and control the geological and engineering factors of the heat transfer characteristics through surrounding rock, But so far, the research in this area is still in the initial stage.In view of this, this dissertation base on the existing research on cold regional tunnel temperature field at home and abroad, relying on the key projects of science and technology research and development program of China Railway "the key technology research on protection and drainage of high speed railway tunnel in cold region". Selecting Wafangdian tunnel of Beijing to Shenyang Inter-city Train to carry out the field test of temperature.According to the measured temperature data, the evolution law of temperature field in cold regional tunnel and buried deep ditch setting were studied in detail by mathematical derivation and numerical simulation.The main conclusions and outcomes are as following:(1) Formed a set of temperature field of tunnel in cold regional long-term automatic real-time monitoring system with advanced mature computer technology, communication technology, data acquisition technology and sensor technology in one.(2) By analyzing the field test data: ①Temperature field of cold regional tunnel follow the change law of " External changing internal stability ". ②The geothermal gradient of the surrounding rock gradually decreases with the increase of the longitudinal depth and the radial distance of the tunnel.(3) Based on the measured data, the calculation of the basic parameters is back analyzed, the definite conditions of the numerical simulation and the temperature load are determined, and the three-dimensional nonlinear transient numerical simulation of the temperature field is carried out. ①It is considered that the temperature of surrounding rock of tunnel vault is affected by the temperature on lining surface and the atmosphere temperature changing when the tunnel is buried shallow. ②In the middle section of the tunnel, the shape of the isotherm is roughly similar to that of the tunnel section. With the increase of the radial distance, the isotherms become concentric circles.(4) The action law of influence factors of surrounding rock is studied by using the control variable method. The calculation results show that the radius of heat transfer ring of the surrounding rock increases with the increase of thermal conductivity and wall heat transfer coefficient, and decreases with the increase of the initial temperature, specific heat and density of surrounding rock, but the different temperature boundary of the same temperature difference has no effect on it. The maximum heat flux point occurred in the tunnel wall corner, and the relationship between heat flux and temperature difference is a linear increasing function.(5) Modified the theoretical calculation formula of the radius of heat transfer ring of the tunnel with the constant temperature plane model. Orthogonal numerical simulation was introduced to study the sensitivity of various factors affecting the freezing depth and intuitive analysis:The initial temperature of surrounding rock has the greatest influence, followed by thermal conductivity coefficient, density and specific heat, and the influence of wall heat transfer coefficient is the least.(6) The temperature Ts= 0℃ at the interface between the secondary lining and the primary support is proposed as the control condition of the center deep buried ditch under the inverted arch. And It is proved that forecasting the central deep buried ditch is more reliable through loading 3 months by the minimum value of 12-2 monthly average temperature in the winter. Research of different wall temperature, thermal conductivity, initial temperature of surrounding rock corresponding to the track bed frozen depth, and gives some query table, the results of has a certain reference value for center deep buried ditch setting.