Buckling investigation and design consideration for new water tunnel structure

The public water supply line is required to build depth underground in an urban district in recent years. However the construction method has not been completely established especially for a large diameter water tunnel built in the congested urban district. As the latest water tunnel structure the separated-type water tunnel structure composite of steel liner and RC segments linings has been proposed in Japan. However the buckling of steel liner has not been solved which is obstructing the application of new water tunnel structure considering the high hydrostatic pressure is inevitably built up in the void between RC lining and liner during an operation period. In this article the study on buckling of locally supported steel liner encased in RC linings is carried out using the numerical analysis. The encased liner fails in single-lobe buckling and the critical pressure is related to not only the geometries of steel liners but also the initial gap are identified. Meanwhile the existing buckling equations are examined and discussed and the design procedure for locally supported steel liner is presented.