DESIGN METHOD FOR SUPPORT STRUCTURE OF ROAD TONNEL IN COLD REGION CONSIDERING THE DECRESE IN COST OF CONSTRUCTION

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Tunnel lining is designed and constructed mainly based on the past experience. Considering mechanical characteristic to lining and the development of anti-frost method tunnels in cold region lead to a proper structure, and it can reduce the cost of construction. The principal results of this study are summarized as follows :1.Proposal of newly confinement curve : In this study, the newly confinement curve for support (namely stiffness of support) is developed. To this end, the tunnel is idealized as a perfectly cylindrical thin shell with two stiffening steel rings at ends. The mainly results are as follows:(1)The results for the stiffness of support obtained by this study are less than the ones obtained by the thin ring theory; the maximum error is 20 percent.(2)The effect of stiffening steel ring may be presented in terms of an effective width (0.35〜1)L where L is the length between two rings.2.Estimation of temperature overall the length at tunnels in cold region : For heat insulator design at road tunnel in cold region, it is necessary to estimate and/or determine the lowest (periodical) temperatures overall the length at tunnel. An equation for estimating temperature by a theoretical analysis considering heat convection/conduction between the tunnel-ground and the air flow is presented. From this study, the following results are obtained;(1)The calculated values well agree with the observed ones.(2)We can reasonably determine the necessary length of anti-frost treatment from tunnel entrance.