This paper describes the development of a unique pipeline fault crossing design upgrade for a 22-inch (559 mm) diameter Pacific Gas & Electric Company (PG&E) gas transmission line where it crosses the Calaveras fault near Sunol, California. The new design is capable of withstanding significant levels of horizontal fault offset while minimizing the deformation demands experienced by the pipeline. This unique design concept is applicable to fault crossings with well defined fault locations and highly localized fault offset profiles (e.g., for this fault, 85% of the offset is expected to occur within ±5 feet (±1.5 m) from the center of the fault trace, which was precisely located by field trenching studies). Relative to the original fault crossing design, the new design provides a more favorable “local” fault crossing angle “β” (β = 73° for the original design vs. β = 95° for the new design). The angle change is accomplished by installing an offset section of the pipeline adjacent to the fault such that the fault crosses the pipeline in the middle of a tangent section in the nearest offsetting leg. The four bends used to fabricate the offset section are cold bends with an average radius of 76.4 feet (23.3 m). The entire mitigated section of the pipeline is buried in a select sand trench. For this design configuration, right lateral fault motion results in (a) a “closing” action within the two adjacent cold bends located on either side of the fault and (b) a net tension force in the pipe (due to the obtuse β value) centered on the tangent section of the offsetting leg containing the fault crossing. The net tension force in the offsetting leg results in an “opening” action within the two adjacent cold bends on either side of the fault. By adjusting the local fault crossing angle β, the “bend opening” action that results from pipe extension across the fault can be made to nearly offset the “bend closing” action induced by the transverse component of the fault offset. The use of a select sand backfill in the retrofit section allows the bends to engage the soil with relatively low transverse and longitudinal resistance thereby enhancing the overall flexibility/compliance of the fault crossing design. Implementation of this unique design concept at the Calaveras fault crossing increased the amount of fault offset required to damage the pipeline from about 7 inches (18 cm) for the “as-built” design to well over 90 inches (2.3 m) for the retrofit.
Skip Nav Destination
2004 International Pipeline Conference
October 4–8, 2004
Calgary, Alberta, Canada
Conference Sponsors:
- International Petroleum Technology Institute
ISBN:
0-7918-4176-6
PROCEEDINGS PAPER
A Unique Pipeline Fault Crossing Design for a Highly Focused Fault Available to Purchase
Chih-Hung Lee,
Chih-Hung Lee
Pacific Gas & Electric Company, Walnut Creek, CA
Search for other works by this author on:
Frank Dauby,
Frank Dauby
Pacific Gas & Electric Company, Walnut Creek, CA
Search for other works by this author on:
Keith I. Kelson,
Keith I. Kelson
William Lettis & Associates, Inc., Walnut Creek, CA
Search for other works by this author on:
Christopher Hitchcock
Christopher Hitchcock
William Lettis & Associates, Inc., Walnut Creek, CA
Search for other works by this author on:
James D. Hart
SSD, Inc., Reno, NV
Nasir Zulfiqar
SSD, Inc., Reno, NV
Chih-Hung Lee
Pacific Gas & Electric Company, Walnut Creek, CA
Frank Dauby
Pacific Gas & Electric Company, Walnut Creek, CA
Keith I. Kelson
William Lettis & Associates, Inc., Walnut Creek, CA
Christopher Hitchcock
William Lettis & Associates, Inc., Walnut Creek, CA
Paper No:
IPC2004-0102, pp. 291-298; 8 pages
Published Online:
December 4, 2008
Citation
Hart, JD, Zulfiqar, N, Lee, C, Dauby, F, Kelson, KI, & Hitchcock, C. "A Unique Pipeline Fault Crossing Design for a Highly Focused Fault." Proceedings of the 2004 International Pipeline Conference. 2004 International Pipeline Conference, Volumes 1, 2, and 3. Calgary, Alberta, Canada. October 4–8, 2004. pp. 291-298. ASME. https://doi.org/10.1115/IPC2004-0102
Download citation file:
13
Views
Related Proceedings Papers
Related Articles
Stability of Vertically Bent Pipelines Buried in Sand
J. Pressure Vessel Technol (August,2004)
Effect of Transitions in the Water Table and Soil Moisture Content on the Cathodic Protection of Buried Pipelines
J. Pressure Vessel Technol (February,2011)
Effectiveness of Anti-Liquefaction Techniques for Buried
Pipelines
J. Pressure Vessel Technol (August,1994)
Related Chapters
Better Risk Management for Underground Pipelines and Tunnels Using Sound Geotechnical Interpretation
Geological Engineering: Proceedings of the 1 st International Conference (ICGE 2007)
Macropore Spatial Variability of CT-Measured Solute Transport Parameters
Intelligent Engineering Systems through Artificial Neural Networks, Volume 20
Examining the Structure-Function Relationship of Block Copolymer Soil Surfactants in Sand-Based Putting Greens
Pesticide Formulation and Delivery Systems: 42nd Volume, Building the Future of Agrochemicals for 2030 and Beyond