Safety of Buried Pressurized Gas Pipelines near Explosion Sources

Abstract

Accidental explosions in process industries, explosives factories, open pit mines, quarries, public works or even intentional explosions near a pipeline (sabotage) may endanger buried pressurized gas pipelines. Risk estimation is very complicated due to a great deal of phenomena participating in the final output, namely, explosion, energy transfer to the soil and air, soil pipeline interaction, and response of the pipeline. The explosion source analysis was based on theoretical, semi-empirical or complicated computer codes. Stresses on the pipeline were directly related to the peak particle velocity of the ground in contact with the pipeline. The cube root scaling model of the shock wave propagation through soil was used for estimating the attenuation of particle velocity. The relative stiffness of the liner compared to the medium in which it is embedded was also taken into account. A one-step estimation method was developed for the prediction of either safety distance, or maximum allowable quantity of explosives, or pipe equivalent stress induced by ground shock waves generated by the explosion. The method is based on a relationship of attenuation of peak particle velocity with distance pipeline stress models and an experimentally determined relationship between circumferential and longitudinal strains derived from experimental results. The Huber-Hencky-Mises stresses approach was used in the models. The method takes into account the parameters related to explosion source, explosive-to-soil coupling effect, shock wave propagation in the ground, attenuation of ground waves with distance, soil-to-pipe coupling effect, dynamic nature of impact wave and construction characteristics of the pipeline in single solvable formulas for each of the above cases. Scientific calculators can be used to solve these formulas, but estimations can be greatly facilitated by the constructed nomographs or by use of a worksheet prepared in Ms-Excel environment.