Soil-pipeline interaction at Storebaelt
Conference
·
OSTI ID:205470
- Danish Geotechnical Inst., Lyngby (Denmark)
- Dansk Olie- and Gasproduktion A/S, Hoersholm (Denmark)
Storebaelt crossings form a vital part of the Danish Natural Gas Transmission System. The crossings comprise two 30 km long, 30 in. diameter pipelines separated by a distance of 1,800 m. The pipelines were installed during the period 1982--84, primarily in post-trenched ditches which were left for natural backfilling. A comprehensive inspection program on the geotechnical conditions and the pipe condition was initiated in 1986 in order to provide the input for the assessment of the bearing capacity of the soft natural backfilling dominated by silty gyttja. These analyzes of the pipe stability showed that the risk of settlements due to failing bearing capacity in the natural backfilling was negligible because of the fast generation of cohesive strength in soft backfilling, but on the contrary it revealed that a potential risk of flotation and liquefaction at the transition stage from uncovered to fun coverage of the pipelines by soft backfiring existed. The 1986 program was followed by investigations in 1989 and 1991 to pursue this problem, and based on the in situ inspection results and analyzes it was concluded that the risk of the pipe stability being endangered by flotation and liquefaction was negligible, apart from wave induced liquefaction during storms at a limited number of exposed locations. For the future risk assessment a set of relatively simple guidelines for evaluating the stability based on monitoring of sedimentation rates in these areas was established. The parameters are monitored by yearly inspections. So far there has been no need for further corrective measures, such as installation of grout bags.
- OSTI ID:
- 205470
- Report Number(s):
- CONF-950695--; ISBN 0-7918-1311-8
- Country of Publication:
- United States
- Language:
- English
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