Some Investigations on Cracking of the Tunnel in Cold Region

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The project is summarized as follows :(1) Temperature can be defined from homogeneous spatial processes by means of a linear transformation, and the design temperature for tunnel heat insulator can be interpolated by Semi-Variogram using a stochastic algorithm. A comparison of the estimated design temperature and the observed temperature of actual data shows that the proposed method yields very good results.(2) The periodic changes of atmospheric temperature can be transformed to a moving mean value and narrowing amplitude due to distance from the entrance of the tunnel.(3) It is found that data mining procedure using neural network is useful for finding the cause of cracks in the tunnel lining.(4) A numerical method is developed for analyzing for the one-dimensional moving boundary problem in semi-infinite region. The method is useful for determining the depth of the frozen ground behind tunnel lining. A comparison with other solutions suggests that the proposed method provide satisfactory accuracy.(5) In order to investigate the mechanics of thermal cracking in the tunnel lining, heat transfer and stresses are determined using the two-dimensional finite element method and employing interface element for the heat insulator. A concrete model including ageing effects and time-dependent properties is adopted. It is made clear that the elastic modulus of concrete in early ages and thermal conductivity of concrete are sensitive to thermal cracking.