Research On Temperature Field And Heat Insulation Layer Of High Geo-Temperature Railway Tunnel

In recent years, with the development of the national railway, more and more tunnels are built in the area of high geo-temperature. However, due to the research on high geo-temperature tunnel in China start later, there is no corresponding codes that can guide the design and construction of high geo-temperature tunnel. Therefore, it is urgent to speed up the research on the related problems of the high ground temperature tunnel. This paper takes the JI WO XIGA tunnel in the Lasa-Rikaze railway as the research background, and extended to the double track railway tunnel, the temperature field and the heat insulation layer of the high geo-temperature railway tunnel are studied by using the method of theoretical analysis and ANSYS finite element numerical simulation. The main contributions of this dissertation are as follows:1. By means of numerical simulation, the change law of the temperature field of the surrounding rock of the high geo-temperature tunnel with two cross sections is analyzed. The results show that:(1) The radius of the surrounding rock increases with the increase of the ventilation time, but the increase rate decreases with the increase of the ventilation time. (2) In the early stage of ventilation, the distribution of the heat-adjusting layer is related to the shape of the tunnel section, in the late stage of ventilation, the distribution of the heat-adjusting layer is more and more similar to a group of concentric circles, the closer to the inside of the tunnel, the more close to the isotherm distribution. (3) Under the same ventilation time, the relationship between the cooling range of the surrounding rock and the size of the tunnel section is not large.2. Based on the fuzzy evaluation method and the numerical simulation method, the heat insulation layer in the high geo-temperature tunnel is determined. Heat insulating material should be selected silicate composite insulation blanket or dry method of aluminum silicate fiber board. The heat insulation layer should be used in the sandwich laying mode. The smaller the thermal conductivity of the heat insulation layer is better, the thermal conductivity coefficient is determined according to the selected heat insulation material. The thickness of heat insulation layer should be taken 5 cm-10 cm.3. By using the numerical simulation method, the change trend of the temperature of the support structure of the tunnel with the ventilation time is analyzed under the two conditions of the thermal insulation layer. The results show that:the two trends are the same, but the time required for the tunnel support structure to reach the maximum temperature is different in different situations, t (No heat insulation layer)< t (Sandwich type)< t (Two-layer equation)< t (Attach wall type).4. Through the numerical simulation method, the change of the force with the ventilation time of the tunnel support structure under different geo-temperature is analyzed. The results show that:(1) Although the stress value of the supporting structure of the high ground temperature tunnel has changed with the increase of the ventilation time, the position of the extreme value distribution is not changed. And there is an extreme point, in which the stress change of the supporting structure is the largest, and the geo-temperature has the greatest influence. In the engineering background of this paper, the value of the extreme point occur in ninth days of the ventilation time. (2) The position of extreme value distribution of the support structure of tunnel with different geo-temperature is basically unchanged, and the stress change is linear with the increase of geo-temperature. The geo-temperature has a great influence on the tunnel support structure.