Evaluation of Design Requirements for Anchor Block of Buried Pipelines

Document Type : Research Article

Authors

1 Associate Professor, Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran

2 Geotechnical Engineering Consultant

Abstract

Gas transmission pipelines will expand when they are put into operation under the influence of increased internal pressure and temperature. The movement due to such expansion is significant for large diameter pipelines which operate at high pressure and elevated temperature. The pipeline needs to be restrained near compressor stations in order to prevent the transmission of such movement to equipment and facilities within the station. Concrete anchor blocks are commonly used to restrain the movement of buried pipelines on both sides of compressor stations. Anchor blocks for transmission pipelines are usually massive because of the high axial stress in the pipe which results in large thrust force. Current design procedures are usually based on providing an adequate margin of safety against block sliding, block overturning and soil bearing pressure.

This paper presents the results of an analytical study on the response of soil, pipeline and anchor block at different operating pressure and temperatures. Nonlinear finite element analyses which include modeling of soil-pipe and soil-block interactions are carried out to evaluate the design procedures. The results indicate that the concept used in current design procedures is fundamentally flawed because it is based on controlling forces rather displacements. Furthermore, both the thrust force and the resistance capacity are grossly miscalculated. The thrust force is significantly overestimated because it is based on a fully restrained anchor. The resistance capacity of the block which is calculated based on full mobilization of the passive resistance of soil is also drastically miscalculated because only a fraction of the passive resistance is mobilized.

Keywords

Main Subjects

References

Al-Gahtani, H. J. (2009). Optimum design of buried pipeline block anchors. Practice Periodical on Structural Design and Construction. https://doi.org/10.1061/(asce)1084-0680(2009)14:4(190.
American Lifelines Alliance. (2001). Guideline for the Design of Buried Steel Pipe. American Society of Civil Engineers, New York, NY.
ASCE (1984). Guidelines for the Seismic Design of Oil and Gas Pipeline Systems. American Society of Civil Engineers, New York, NY.
Ashrafi, H., Vasseghi, A., Hosseini, M., & Bazli, M. (2019). Development of fragility functions for natural gas transmission pipelines at anchor block interface. In Engineering Structures (Vol. 186). Elsevier BV. https://doi.org/10.1016/j.engstruct.2019.02.020.
Caltrans (2006). Seismic design criteria. SDC-2006, California Dept. of Transportation, Sacramento, Calif.
Das, B. M. (2002). Principles of Geotechnical Engineering, 5th edition. In Brooks/Cole eBooks. http://ndl.ethernet.edu.et/bitstream/123456789/33343/1/7.pdf.
Duncan, J. M., & Mokwa, R. L. (2001). Passive Earth Pressures: Theories and tests. Journal of Geotechnical and Geoenvironmental Engineering, 127(3), 248–257.
Liang-Chung, P. (1978). Stress Analysis Methods for Underground Pipe Lines-Part 1: Basic Calculations. Pipe Line Industry.
Liang-Chung, P. (1978). Stress Analysis Methods for Underground Pipe Lines-Part 2: Soil-Pipe Interaction. Pipe Line Industry.
PRCI (2009). Pipeline Integrity for Ground Movement Hazards. Houston: Pipeline Research Council International.
Rollins, K.M. and Sparks, A. (2002). Lateral Resistance of Full-Scale Pile Cap with Gravel Backfill. Journal of Geotechnical and Geoenvironmental Engineering, 128(9), 711-723.
Stewart, J. P., Taciroglu, E. Wallace, J. W, Ahlberg, E. R., Lemnitzer, A., Rha, C.,  et al. (2007). Full Scale Cyclic Testing of Foundation Support Systems for Highway Bridges: Part II: Abutment Backwalls. UCLA: Civil and Environmental Engineering.
Wijewickreme, D., Karimian, H., & Honegger, D. H. (2009). Response of buried steel pipelines subjected to relative axial soil movement. Canadian Geotechnical Journal, 46(7), 735–752. https://doi.org/10.1139/t09-019
Wood, J. H. (2009). Resistance from bridge abutment passive soil pressure in earthquakes. Proceedings NZSEE Annual Conference.
Zhang, L., Yan, X., & Yang, X. (2016). Using the unit force method to analyze thrust acting on anchor blocks caused by thermal expansion displacement of X80 tunnel pipelines. Journal of Pipeline Systems Engineering and Practice, 7(1). https://doi.org/10.1061/(asce)ps.1949-1204.0000202.
Journal of Seismology and Earthquake Engineering
Volume 23, Issue 4
November 2021
Pages 37-50

Files

Share

How to cite

Statistics