A Theoretical Evaluation of the Backfill Effect in Fracture of Gas Pressurized Pipelines

Abstract

The constraining action exerted by the soil surrounding pipelines, when an axial fracture propagates, has been analyzed through a simplified model. In order to avoid large-scale numerical computations, two main hypotheses have been assumed: (a) the deformed configuration of the fractured pipe has been considered as defined by two geometrical parameters; (b) the soil has been schematized as a cohesionless medium composed of rigid particles with friction. The energy absorption rate by soil during fracture propagation and the constraining forces on the pipe walls has been obtained as a function of the fracture speed and acceleration, of kinematic and geometric parameters and of the soil properties. Available experimental data give factors supporting the engineering evaluation of the backfill effect developed in the paper.