Theoretical study on buckling of deep water pipeline under external hydrostatic pressure

Generally, the main water pipeline is built through installing steel pipes or iron pipes inside a shield tunnel or NATM tunnel and filling the annular void to form an integrated structure. However, the problem of buckling of inner pipe exists for such a structure because the most of the existing filling technologies fail to produce a tightly fitted liner. When the water pipeline is built deep underground, the separated structure should be adopted in order to ensure the minimum cross section of the tunnel as well as the safety of water pipe. In this study, the buckling of stiffened water pipe used for separated structure is investigated. Firstly, the formulas of general buckling and local buckling are derived with Ritz method, and the methods of the formulas application are given in terms of the critical pressure calculation and the buckling behavior simulation. Secondly, the methods are verified by numerical analysis and existing experiments. Finally, the local buckling design method for separated water pipeline structure is proposed, taking into account of the buckling characters of a practical water pipeline.