Study On Mechanics Characteristic Of Tunnel Lining Constructure In High Geo-Temperature Region

There are6tunnels located along the Lhasa-Rikaze railway geothermal anomalous area, with a total length of30418m, the preliminary investigation reveals that the geo-temperature or water temperature can be as high as80癈, which have a significant impact on the safety and durability of tunnel lining,and put forward new and higher requirements on the lining structure type etc. But the present tunnel and concrete specifications have no related contents, and there are very few successful cases for reference. Therefore, it is very necessary to study on the mechanical properties and the safety of the tunnel lining structure in high geo-temperature region. According to the geological prospecting data and the measured temperature data from the tunnel job site, aimed at the high geo-temperature problem in the tunnel construction process of the Lhasa-Rikaze railway, researches are carried out on the following aspects through the method of numerical simulation:(1) According to the degree of thermal damage in different sections, we suppose the geo-temperature of the tunnel arch springing is48℃,60℃and80℃in three cases,studied the influence on temperature field of different construction stage,and compared the different influence on surrounding temperature field with the steel arch in the preliminary support or not.(2) According to the degree of thermal damage in different sections, we suppose the geo-temperature of the tunnel arch springing is48℃,60℃and80℃in three cases, studied the influence on plastic zone, displacement and preliminary support stress of different construction stage, evaluated the safety of the supporting structure by using the maximum principal stress, and compared them with the case don’t consider the thermal stress, confirmed the critical temperature of the tunnel preliminary support to destruction.(3) Additional thermal stress generated by high geo-temperature can cause the secondary lining cracking, adversely affect the safety and durability of the structure. Based on the thermal damage classification, in order to compare the effect of rock pressure and thermal stress on the secondary lining, using the indirect method analysed the cases when the temperature is38℃,40℃,45℃and50℃outside the secondary lining,and compared them with the case don’t consider the thermal stress,we can get the law of the secondary lining to destruction and confirm the critical temperature.