Response of buried steel pipelines subjected to relative axial soil movement

Abstract

The performance of buried steel pipelines subjected to relative soil movements in the axial direction was investigated using full-scale pullout testing in a soil chamber. Measured axial soil loads from pullout testing of pipes buried in loose dry sand were comparable to those predicted using guidelines commonly used in practice. The peak values of axial pullout resistance observed on pipes buried in dense dry sand were several-fold (in excess of 2 times) higher than the predictions from guidelines; the observed high axial pullout resistance is primarily due to a significant increase in normal soil stresses on the pipelines, resulting from constrained dilation of dense sand during interface shear deformations. This reasoning was confirmed by direct measurement of soil stresses on pipes during full-scale testing and numerical modeling. The research findings herein suggest that the use of the coefficient of lateral earth pressure at-rest (K0) to compute axial soil loads, employing equations recommended in common guidelines, should be undertaken with caution for pipes buried in soils that are likely to experience significant shear-induced dilation.

Estimating earth loads on buried pipes under axial loading condition: insights from 3D discrete element analysis

“…The results show a consistent agreement between the estimated and calculated values with a maximum difference of 6%. Wijewickreme et al [39] suggested that when using Eq. (1) to find the axial resistance in compacted sand, K value should be considered within a range between K 0 and 2.5.…”

“…[2,7,10,18,21,25,26,[37][38][39]. Roy et al [33] used finite element (FE) analysis to model soil-pipe interaction in dense sand subjected to lateral ground displacements.…”

Axial friction response of full-scale pipes in soft clays

“…The u is used to express the ultimate axial friction coefficient and determined based on ultimate axial resistances using Eqs. (2), (3) and (5). The r is used to express the residual axial friction coefficient and determined based on residual axial resistances using Eqs.…”

“…The subsea pipelines in soft clays generally operate at relatively high pressures and temperatures during transporting oil or gas. These conditions require pipeline to be designed to buckle in a controlled manner during its service life, especially the phase of startup and shutdown [1][2][3][4]. The axial friction resistance of pipelines has a significant impact on the axial buckling design of subsea pipelines in soft clays.…”

“…In attempting to obtain the friction coefficient of pipelines, theoretical and experimental researches are available. Many researches focused on the interaction of pipe with cohesionless soil over the past several decades [2,[10][11][12][13][14][15]. Only a minority of scholars studied the pipe-clay interaction using model tests.…”