Modeling the effect of backfill on dynamic fracture propagation in steel pipelines

Abstract

In this paper, dynamic ductile fracture propagation simulations were conducted to study the use of smoothed particle hydrodynamics (SPH) for modeling the effects of backfill in pipeline burst simulations. The effect of SPH parameters on fracture velocity was studied using the Battelle Two-Curve Method (BTCM) approach of decoupling mechanics and gas decompression but characterizing propagation toughness by crack tip opening angle (CTOA) rather than Charpy absorbed energy (CVN). The backfilled pipe model was developed and studied using the commercial finite element code ABAQUS 2017. Ductile fracture propagation was simulated using a shell based constant CTOA model. The current study examined the numerical aspects of applying SPH through comparing results with literature. The effects of particle size, various backfill material properties, and backfill depth on the fracture velocity were examined. It was found that the particle size had a minor effect on the fracture velocity and should be selected in proportion to the diameter of the pipe being examined. The numerical study showed that increasing the density and shear modulus of the backfill material resulted in a reduction of the fracture velocity. The effect of backfill depth up to 1.4 m was also examined numerically and found to have little effect on the fracture velocity, agreeing well with literature. The present study illustrates the sensitivity of the fracture velocity to the various parameters used in SPH models.

Keywords

• Dynamic ductile fracture
• Steel pipelines
• Backfill
• CTOA criterion
• FEA