Open Collections

Jayasinghe, Thushara Dilrukshi

University of British Columbia

Organic soils (i.e., muskeg, peat deposits) cover 5 to 8% of the land surface of the earth, and in Canada, many energy pipelines cross these soils over large distances. Thermal changes due to operational and environmental reasons pose a significant threat to the structural integrity and safety of pipeline systems in these soils. Engineering design of pipelines in muskeg terrains involves many challenges, mainly due to the lack of understanding of the mechanical behavior of organic soils. Such knowledge gaps have caused an absence of well-adapted soil-pipe interaction (SPI) assessment methodologies for pipeline design in organic soils, unlike the methods readily available for pipes buried in mineral sandy and clayey soils (e.g., PRCI 2009). For these reasons, pipeline designs in organic soils are often conducted with significant conservatism. A research study is undertaken to characterize organic soils primarily using geotechnical field investigation tools and obtain representative strength and stiffness parameters for SPI analysis. It was found that the ball penetrometer test (BPT) is effective as a field testing tool for investigating organic soil along pipeline corridors. A reasonable stress-strain (constitutive) model to represent organic soils in numerical modeling was selected by validating with respect to data from field pressuremeter testing, and in turn, that model was employed to simulate SPI problems. High-quality experimental datasets on axial and lateral loading SPI mechanisms in pipes buried in organic soil were developed based on results obtained through full-scale physical modeling. The lateral SPI of pipes buried in organic soils was modeled numerically, and the developed SPI model was verified using full-scale physical testing results to justify its suitability for engineering evaluations. Using the validated numerical framework, a series of pipeline configurations were simulated to reach a comprehensive understanding of lateral SPI in organic soils. Considering the comparisons of load-displacement response from numerical analysis and/or full-scale experimental results with those arising from equations proposed in current pipeline guidelines, recommendations are made for modifying the total stress approaches specified in PRCI guidelines (2009) for soft clayey soils to assess axial and lateral soil restraints on pipes buried in organic soils.

Text

2024-04-17

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87862

Civil Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/