Soil Mechanics for Stress Analysis and Pipeline Design
Purpose:
The purpose of this one-day seminar/workshop is to educate pipe stress engineers and analysts, mechanical engineers and non-geotechnical engineers regarding general principles of soil mechanics and geological hazards as they relate to the design and stress analysis of pipelines. In many cases the communication between the pipe stress team and the geotechnical engineers is weak and complicated by miscommunications and misunderstanding of technical terms on both sides.
Following this seminar, the participant will have a strong grasp of basic geotechnical definitions and soil mechanics and understand how the equations used to develop soil-springs and yield displacements are derived from geotechnical and foundation engineering analogies. The stress engineer will understand the issues and limitations of soil mechanics as they relate to pipe stress analysis and be able to communicate with the geotechnical engineers on an informed level. Through the use of numerous case histories and examples, the concepts of soil mechanics as they interact with pipeline design are illustrated.
Outline of Presentation:
1. Soil classification and definitions
- ASTM D2487/ASTM2487
- Other classification systems, (e.g., Eurcode, SNiP/GOST)
- Definitions and descriptions
- Soil laboratory tests
- Typical soil properties
- Effect of ground water and pore water pressures
2. Geotechnical Investigations for pipeline design and analysis
3. Soil – pipeline interaction scenarios
- Ground movement events
- Lateral spreading (liquefaction) and sensitive soils
- Upheaval buckling
- Frost heave and thaw settlement
- Thermal expansion issues
4. Soil strength testing and interpretation
- Effective stress principle
- Drained versus undrained strengths
- Effective stress versus total stress strengths
- Soil tests and deformation plots
- Mohr Circles and stresses
- Field interpretation of soil strength
- Strength correlations to soil index properties
- Strength of peat and organic deposits
5. Pipeline deformation scenarios
- Examples of soil-pipe interactions
6. Maximum soil strength derivation and soil pipe interaction relationships
- Strength and deformation relationship development
- Maximum soil strength and yield displacements
- Bilinear versus hyperbolic soil strength-displacement relationships
- Spring constants
- Special consideration for organic deposits and peat soils
7. Soil-Pipe Interaction Considerations
- Conservatism in soil parameter selection
- Unsaturated soil mechanics and pipeline interaction
- Deep burial (HDD)
- Settlement over HDD installations
- Effect of trench width
- Effect of backfill properties
- Virtual anchor effects
- Pipelines on slopes
- Applied Delta-T and lock-in temperatures
- Strain softening in soil strength
- Soil-pipe loading rate effects – drained versus undrained soil loading
8. Monitoring and Mitigation
9. Summary and key messages
Pipe stress engineers/ analysts, and mechanical and pipeline engineers who use geotechnical information in the design and analysis of pipelines; geotechnical engineers who support pipeline design.
Dr. Oswell has worked on many pipeline projects in western and northern Canada, and internationally for nearly 40 years. Many of these projects involved site investigations, laboratory testing, extensive analysis and evaluation and development of engineering study reports.
Dr. Oswell has extensive pipeline geotechnical engineering and geological hazard assessment experience. He provided specialist permafrost engineering for pipeline projects in northern Canada, Alaska, and Russia. He is presently part of the Strain Based Design team for the Alaska LNG pipeline project. He has senior consulting experience on the following major pipeline projects: Mackenzie Gas Project (Canada), Norman Wells oil pipeline (Canada), Alaska North Slope Project (United States), Denali Pipeline Project (United States, Canada), Alaska Gas Project (United States, Canada), Mohe-Daqing oil pipeline (China), Baydaratskaya Bay Gas Pipeline Crossing (Russia), the ExxonNeftigaz Sakhalin to DeKastri oil pipeline (Russia) and the Sabah-Sarawak gas pipeline (SSGP) in east Malaysia.
As an expert in geohazards interaction with pipelines, Dr. Oswell conducted studies or acted as a senior reviewer/advisor for projects with significant engineering and technical challenges such as geohazard management including landslides, earthquake faults, and liquefaction. He has experience in the interpretation of geological hazards in LiDAR imagery. He is a recognized
expert in geotechnical issues related to soil-pipe interaction. He has further experience in strain-based design issues for pipeline design, and geological hazard (risk) assessment. He has conducted geoforensic investigations involving pipeline integrity issues in Canada, United States Ecuador, and Colombia. He is presently retained as an expert witness in several pipeline ruptures cases in Canada and the United States.
Publications
Dr. Oswell has published over 30 technical conference and peer-reviewed journal papers, and was the keynote speaker at the 63rd Canadian Geotechnical Conference/6th Canadian Permafrost Conference. He is formerly an Associate Editor of the Canadian Geotechnical Journal and member of the ISO Committee ISO/TC067/SC02/WG23 "Geological hazards risk management of onshore pipelines”.
- Soil mechanics for pipeline stress analysis, ISBN: 978-0-9952410-1-85 in fall 2021
Other important contributions include two chapters to a 2019 ASME publication:
- Oswell, J.M. 2019. Chapter 10. Geotechnical aspects of pipelines in permafrost. In Pipeline Geohazards: Planning, Design, Construction and Operations. Edited by Moness Rizkalla and Rod Read. American Society of Mechanical Engineers Press, New York. ISBN: 9780791861790.
- Oswell, J.M. 2019. Chapter 9. Erosion and sediment control of pipeline right-of-ways. In Pipeline Geohazards: Planning, Design, Construction and Operations. Edited by Moness Rizkalla and Rod Read. American Society of Mechanical Engineers Press, New York. ISBN: 9780791861790.
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