Full-Scale Physical Modeling of Axial Soil-Pipe Interaction in Organic Soils

Abstract Organic soils (i.e., muskeg, peat deposits) cover 18% of the Canadian landscape and many energy pipelines cross these soil terrains 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/clayey soils (e.g., PRCI guidelines [1]). In view of the above, a detailed research program is undertaken to study the soil-pipe interaction in organic soils. As a part of this program, a series of full-scale axial pipe displacement tests was conducted using a sand blasted 114 mm diameter steel pipe buried in organic soil simulating different H/D ratios, directly yielding axial p-y curves (i.e., soil springs). The “soil springs” representing muskeg are compared with those computed using equations given in PRCI guidelines [1] for pipes buried in clayey soils. Based on this, adjustments to these clay-based equations are proposed for generating axial soil springs for pipes buried in organic soils.