Trench effects on lateral p-y relations for pipelines embedded in stiff soils and rocks

Abstract

Existing relationships for lateral backfill pressures on pipelines assume that the trench is adequately wide to contain the failure surface. This condition is commonly violated in design and construction practice, putting at risk the pipeline safety. In this context, size and shape effects for trenches excavated in stiff soils and rocks, are numerically investigated, through experimentally-calibrated parametric analyses. It is shown that, for narrow trenches, ultimate pressures and yield displacements may increase up to an order of magnitude compared to "infinite-trench" values, while excavation of inclined walls reduces the above detrimental effects. Simplified relations are developed to aid pipeline design.

Safety of buried steel natural gas pipelines under earthquake-induced ground shaking: A review

“…Notably, the effect of pipeline steel scour on the SPI has also been investigated [113] and it was found that tangential interaction depends on the unsupported length of the pipe due to scour. Further, Chaloulos et al [108,109] and Kouretzis et al [110] explored the effect of a narrow trench on the evolution of the soil failure surface and peak pipeline force under lateral pipeline motion. Using experimentally validated numerical models, they show that the commonly used assumption of an infinitely wide trench can lead to underestimation of the actual response quantities.…”

“…Vazouras and Karamanos[107] extended the previous models to study the mechanical performance of pipe bends; their results substantiated their increased flexibility. Chaloulos et al[108,109] and Kouretzis et al[110] employed 2D plane-strain soil-pipe FE models with interface contact elements to study the trench effects on the soil-pipe response subject to PGD. In analytical treatments of pipelines under PGD problems, Karamitros et al[95], adopted a BNWF model and a secant modulus solution method to develop a design methodology to estimate inelastic pipeline axial and bending strains generated by strike-slip fault movement, while Trifonov and Cherniy[111] contributed a plane-stress plasticity model that accounts for internal pressure, temperature variation and bending stresses, combined with a BNWF pipeline model to effectively predict the inelastic stress and strain distributions over the pipe cross-section due to fault displacements.…”

A critical review on the vulnerability assessment of natural gas pipelines subjected to seismic wave propagation. Part 2: Pipe analysis aspects

“…The dimensions and stiffness of the trench soil are other parameters that might also affect the seismic response of a buried pipeline. The commonly used assumption of an infinitely large trench may lead to an underestimation of the actual response of a pipeline subjected to lateral ground seismic motion, as highlighted by Kouretzis et al (2013) and Chaloulos et al (2015Chaloulos et al ( , 2017. Figure 4 elaborates on the effect of trench soil stiffness on axial compression response of embedded steel pipelines.…”

Assurance of Precision for Geometric Dimensions of Trench During Pipeline Development

“…Для обеспечения требований, предъявляемых к траншеям при их возведении под различные коммуникации, согласно строительным правилам [4] предусмотрены устройства для удерживания стенок траншеи от обрушения, а также строительство откосов. Обычно это необходимо в случаях работы в грунтах, подверженных осыпанию (например супесь), и когда необходимо выполнять работы непосредственно в траншее [5]. Но существуют траншеи и условия, когда допускается строительство без удерживающих устройств и откосов [6], например траншеи с вертикальными стенками без креплений на глубину до трех метров при производстве работ роторными и другими траншейными экскаваторами в связных грунтах (суглинках, глинах) согласно рекомендациям [7], [8].…”