Acoustic emission sensing of pipe-soil interaction: Development of an early warning system for buried pipe deformation

This paper describes a programme of research that aims to develop a continuous, real-time acoustic emission (AE) monitoring system that can be distributed at discrete locations along buried pipelines to sense pipe/soil interaction and provide early warning of adverse behaviour to enable targeted and timely interventions. Pipe/soil interaction-generated AE propagates as guided waves along pipelines. Novel AE interpretation is allowing the evolution of the pipe/soil interaction behaviour to be characterised, and the rate and magnitude of deformation to be quantified. New understanding of AE propagation and attenuation in buried pipes is enabling source localisation methodologies to be developed. Results from normal faulting experiments performed on buried full-scale steel pipes at the buried infrastructure research facility at Queen’s University, Canada, are presented to demonstrate the potential of the AE technique for early detection of buried pipe deformation

Use of the WHO Access, Watch, and Reserve classification to define patterns of hospital antibiotic use (AWaRe): an analysis of paediatric survey data from 56 countries

BACKGROUND: Improving the quality of hospital antibiotic use is a major goal of WHO's global action plan to combat antimicrobial resistance. The WHO Essential Medicines List Access, Watch, and Reserve (AWaRe) classification could facilitate simple stewardship interventions that are widely applicable globally. We aimed to present data on patterns of paediatric AWaRe antibiotic use that could be used for local and national stewardship interventions. METHODS: 1-day point prevalence survey antibiotic prescription data were combined from two independent global networks: the Global Antimicrobial Resistance, Prescribing, and Efficacy in Neonates and Children and the Global Point Prevalence Survey on Antimicrobial Consumption and Resistance networks. We included hospital inpatients aged younger than 19 years receiving at least one antibiotic on the day of the survey. The WHO AWaRe classification was used to describe overall antibiotic use as assessed by the variation between use of Access, Watch, and Reserve antibiotics, for neonates and children and for the commonest clinical indications. FINDINGS: Of the 23 572 patients included from 56 countries, 18 305 were children (77·7%) and 5267 were neonates (22·3%). Access antibiotic use in children ranged from 7·8% (China) to 61·2% (Slovenia) of all antibiotic prescriptions. The use of Watch antibiotics in children was highest in Iran (77·3%) and lowest in Finland (23·0%). In neonates, Access antibiotic use was highest in Singapore (100·0%) and lowest in China (24·2%). Reserve antibiotic use was low in all countries. Major differences in clinical syndrome-specific patterns of AWaRe antibiotic use in lower respiratory tract infection and neonatal sepsis were observed between WHO regions and countries. INTERPRETATION: There is substantial global variation in the proportion of AWaRe antibiotics used in hospitalised neonates and children. The AWaRe classification could potentially be used as a simple traffic light metric of appropriate antibiotic use. Future efforts should focus on developing and evaluating paediatric antibiotic stewardship programmes on the basis of the AWaRe index. FUNDING: GARPEC was funded by the PENTA Foundation. GARPEC-China data collection was funded by the Sanming Project of Medicine in Shenzhen (SZSM2015120330). bioMérieux provided unrestricted funding support for the Global-PPS

Finite element analysis of buried steel pipelines under strike-slip fault displacements

The present paper investigates the mechanical behavior of buried steel pipelines, crossing active strike-slip tectonic faults. The fault plane is vertical and crosses the pipeline axis at a certain angle. The interacting soil-pipeline system is modelled rigorously through finite elements, which account for large strains and displacements, nonlinear material behavior and special conditions of contact and friction on the soil-pipe interface. Steel pipelines of various diameter-to-thickness ratios, and typical steel material for pipeline applications (API 5L grades X65 and X80) are considered. Most of the numerical results in the paper refer to the case where the fault plane crosses the pipeline axis at right angle. In particular, the paper investigates the effects of various soil and pipeline parameters on the mechanical response of the pipeline, with particular emphasis on pipe wall failure due to "local buckling" or "kink-ing" and pipe wall rupture. The effects of shear soil strength and stiffness are also investi-gated. Furthermore, the influence of the presence of pipeline internal pressure on the mechanical response of the steel pipeline is examined. Numerical results aim at determining the fault displacement at which the pipeline failure occurs, and they are presented in a graphical form that shows the critical fault displacement, the corresponding critical strain versus the pipe diameter-to-thickness ratio. Furthermore, results for cases where the fault plane crosses the pipeline axis at an angle different that 90-degress are presented and the corresponding failure modes are identified. It is expected that the results of the present study can be used for efficient pipeline design in cases where active faults are expected to impose significant ground-induced deformation to the pipeline

Structural behavior of buried pipe bends and their effect on pipeline response in fault crossing areas

Pipe bends, often referred to as “elbows”, are special pipeline components, widely used in onshore buried steel pipelines. They are sensitive to imposed deformations and their structural behavior is quite flexible and associated with the development of significant stress and strain, which may lead to failure. In the present paper, the mechanical performance of buried steel pipeline bends is investigated first, using rigorous finite element models that account for the pipe-soil interface. Three 36-inch-diameter pipe elbows are considered, subjected to pull-out force and embedded in cohesive soils. The elbows have bend angles equal to 90°, 60° and 30°, and bend radius-over-diameter ratio (R/D) equal to 5. The results show the increased flexibility of the pipeline bend with respect to the straight pipe, and are reported in the form of force–displacement diagrams. Furthermore the deformation limits of each elbow are identified in terms of appropriate performance criteria. The second part of the paper investigates the effect of pipe bends on the response of pipelines crossing active faults using a three-dimensional rigorous finite element model. The numerical results refer to a 36-inch-diameter pipeline crossing a strike-slip fault, and show that the unique mechanical response of pipe bends, in terms of their flexibility, may offer an efficient tool for reducing ground-induced deformations. The three-dimensional model employs the load–displacement curves of the first part of the paper as end conditions through nonlinear springs. Furthermore, the results show that there exist an optimum distance of the elbow from the fault plane, which corresponds to the maximum allowable ground displacement. Therefore, pipeline elbows, if appropriately placed, can be employed as “mitigating devices”, reducing ground-induced action on the pipeline at fault crossings. © 2017, The Author(s)

Thermal Upheaval Buckling of Buried Pipelines: Experimental Behavior and Numerical Modeling

Pipelines transporting oil and natural gas may experience upheaval buckling due to substantial compressive forces induced by high temperature and pressure of the fluid content. Such upheaval buckling may pose a major threat to the structural integrity, safety, and operability of pipelines. This study presents results from a series of scaled physical model tests conducted to investigate the uplift behavior and upheaval buckling of buried pipelines. The first set of experiments investigated the resistance force during vertical pullout for different pipe geometries, embedment depths, and relative densities of sand. The second set of experiments investigated the development of global upheaval buckling due to high axial compression of a buried pipe. The study examined the effect of embedment depth on the buckling characteristics and the postbuckling behavior of the pipe. Numerical analyses simulated the experiments and validated the numerical models. A parametric investigation based on rigorous numerical simulations examined the effect of trench-base initial imperfection, internal pressure, and soil strength on the upheaval buckling resistance. The results showed that as the geometric imperfection amplitude increased and its distribution length decreased, the upheaval buckling resistance substantially decreased. Similarly, an increase of the internal pressure of the pipeline may significantly decrease upheaval buckling resistance. © 2020 American Society of Civil Engineers

Numerical simulation of buried steel pipelines under strike-slip fault displacements

The paper examines the structural response of buried butt-welded steel pipelines, crossing active strike-slip tectonic faults, which are vertical and perpendicular to the pipeline axis. The interacting soil-pipeline system is simulated with finite elements, accounting for large strains and displacements, nonlinear material behaviour, as well as for contact and friction on the soil-pipe interface. Steel pipelines of various diameter-to-thickness ratios, and typical steel material for pipeline applications (API 5L grade X65) are considered. The paper investigates the effects of various soil and pipeline parameters on the mechanical response of the pipeline, with emphasis on pipe wall "kinking" or fracture. The effects of cohesive and non-cohesive soils are also investigated. Furthermore, the influence of internal pressure on the structural response of the steel pipeline is examined. The numerical results are aimed at determining the fault displacement at which the pipeline failure occurs, they are presented in a graphical form showing the critical fault displacement, the corresponding critical strain versus the pipe diameter-to-thickness ratio, and can be used for efficient pipeline design against significant ground-induced deformations due to active strike-slip faults. © 2011 ASCE

Structural performance of buried steel pipelines crossing strike-slip faults

The performance of pipelines subjected to permanent strike-slip fault movement is investigated by combining detailed numerical simulations and closed-form solutions. A closed-form solution for the force-displacement relationship of a buried pipeline subjected to tension is presented and used in the form of nonlinear springs at the two ends of the pipeline in a refined finite element model, allowing an efficient nonlinear analysis of the pipe-soil system at large strike-slip fault movements. The analysis accounts for large deformations, inelastic material behaviour of the pipeline and the surrounding soil, as well as contact and friction conditions on the soil-pipe interface. Appropriate performance criteria of the steel pipeline are adopted and monitored throughout the analysis. It is shown that the end conditions of the pipeline have a significant influence on pipeline performance. For a strike-slip fault normal to the pipeline axis, local buckling occurs at relatively small fault displacements. As the angle between the fault normal and the pipeline axis increases, local buckling can be avoided due to longitudinal stretching, but the pipeline may fail due to excessive axial tensile strains or cross sectional flattening. Copyright © 2014 by ASME