Probabilistic performance assessment of airtightness in concrete tube structures

A Super-speed Tube Train (SSTT) system is considered to be an alternative transportation system where trains could operate as fast as 700 km/h by reducing the air resistance in a vacuum tube structure. One of the most important technical requirements for design of SSTT system is assuring the airtightness in vacuum tube structures. In this paper a probabilistic analysis is performed to assess the airtightness performance of concrete vacuum tube system based on the analytical model and experimental tests. Uncertain design variables related to the airtightness of SSTT system were defined as random variables and specific probability distributions were assigned. The behavior of the internal pressure rise of a concrete tube structure was then probabilistically anticipated using stochastic analyses. The results of the analysis confirm that a probabilistic approach is fundamentally essential to the reliable airtightness evaluation of vacuum tube systems. In addition, a sensitivity analysis performed showed that among the variables considered the mean value of the air permeability due to system discontinuity and the pressure outside a tube structure have the most significant effects on the reliability of a system's airtightness.