Movement Due to Heave and Thaw Settlement of a Full-Scale Test Chilled Gas Pipeline Constructed in Fairbanks Alaska
Notice bibliographique
Résumé
Abstract In this paper the authors report the heave and thaw settlement properties ofa test chilled gas pipeline. A full-scale field experiment of the chilled gaspipeline system was conducted in Fairbanks Alaska from 1999 to 2005. The lengthof the test pipeline was 105m and the diameter was 0.9m. The circulated chilledair was -10 °C. One-third of the pipeline was buried in permafrostand the rest of it was placed in non-permafrost. At the end of July 2003, circulation of the chilled air ceased, however, monitoring of the thawsettlement properties of the test pipeline continued until the middle of April,2005. The results obtained include:As the frost-bulb around the pipeline innon-permafrost section formed, the test pipeline in the non-permafrost sectionmoved upward, resulting in bending of the pipeline at the boundary.Insummers, overburden frozen ground of the pipeline became thinner due to thedevelopment of active layer above. The pipeline buried in permafrost sectionmoved upward abruptly, fracturing the thinning overburden frozen ground.Thephenomenon mentionedoccurred successive summer, and the pipeline uplift inpermafrost section continued in summers.In relation withthe upwardmovement in non-permafrost section was confirmed by frost heaving of the pipefoundation.Settlement of the test pipeline was also confirmed by thawsettlement of the foundation.During the thawing process, the temperature ofthe thawing frost bulb became 0 °C at first and then thawed rapidlyin summer together with the development of active layer. As a result, settlement of the pipeline happened rapidly in summer. Introduction In the existing natural gas production field in permafrost regions such asWest Siberia, gas pipelines float in water or are exposed in ditchs as shown inthe photos of Fig. 1. However the gas pressure at the present time has droppedconsiderably comparing to the one in the initial production days. This pressuredrop enables the damaged pipeline system to survive. However, those initiallyburied gas pipelines are now mostly exposed and lost the structural stabilitiesand security reliability. As for the natural gas pipeline installation in permafrost regions, theburied system has been recommended for security reasons. In order to preventthawing of the permafrost shown in Fig. 1, the gas must be chilled fortransportation in permafrost regions. On the other hand, even with the chilledgas pipeline system, miner problems may still happen in limited sections of thepipeline where frost heave damage occurs when the pipeline freezessurrounding soils in non-permafrost section (Talik). Two primary chilled pipeline test experiments are discussed in theliterature: the Calgary Frost Heave Facility and the Caen, France experiment. Athird chilled pipeline experiment was conducted at the Fairbanks Frost HeaveFacility, but the data remains unavailable to the public. The Caen, France chilled pipeline experiment is well documented in public literature byGeotechnical Science Laboratories (1983, 1986a, 1986b, 1988) and Dallimore andWilliams (1985). The purposes of the Caen experiment were toinvestigate differential heave resulting from the abrupt transitionbetween two different lithologic soils (Caen silt and SNEC sand) with varyingfrost susceptibilities and the associated stresses incurred by the pipeline andthe soil mass. Abrupt lithologic transition zones are common in thenatural environment such as the transition between active fluvial graveldeposits and silt overbanks deposits.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».