Experimental investigation of buckling collapse of encased liners subjected to external water pressure

This report presents the experimental results of a comprehensive investigation on the buckling of an encased liner under external water pressure. The pre- and post-buckling behaviours of tightly and loosely fitted liners, as well as their collapse mechanism, were investigated by performing a series of experiments using novel pressurizing equipment. The experimental results clearly show that an encased liner can collapse due to inelastic single-lobe buckling or elastic buckling, depending on the liner and constraint conditions. In addition, the existing related solutions are discussed, and it is identified that none of the solutions can appropriately evaluate the critical pressure for both tightly and loosely fitted liners. Moreover, recent buckling accidents are discussed, and suggestions for safe design are presented.