Pipeline Integrity in Seismic and Extremely Cold Regions

This paper discusses seismic integrity of a gas pipeline in extremely cold regions which pipeline consists of X70-grade high-strain line pipes with outside diameter of 1420 mm. Longitudinal compressive strain limits and max longitudinal compressive strain induced by compressive or bending deformation are discussed. The strain capacity in bending of the high strain line pipes tends to be high by 0.5% compared to the largest value within those calculated by some semi-empirical formulae proposed by former researchers. The pipeline may be subjected to axial and/or bending deformation due to ground deformations in discontinuous permafrost zones or stone run areas before an earthquake occurs there. Hence the effects of ground motion and ground deformations should be taken into account simultaneously to investigate the seismic integrity of a pipeline. In order to simply distinguish displacement controlled condition from load controlled condition, parameters including pipe-soil interaction properties are proposed. Design formulae were derived to calculate strain demand of a pipeline to endure the ground deformations, which parameters shall be applied to the deformation in the displacement controlled condition. Finally it was concluded that the high-strain pipes are effective to ensure pipeline integrity in extremely cold and seismically active regions.