District heating (DH) systems are commonly used in urban areas to distribute thermal energy from central heat sources. Buried pipes, with a composite cross-sectional construction, are used transport a heated medium, usually water. These pipes expand and contract radially and axially due to changing water temperatures, invoking soil-pipe interaction situations during operation, and potentially leading to significant pipeline material strains. A series of full-scale tests were undertaken to specifically investigate the influence of thermal expansion on axial pullout resistance using DH pipes buried in sand in a full-scale soil-pipe interaction test chamber. During testing, the pipe is filled with water that is subjected to temperature changes to simulate field conditions. Axial pipe pull-out tests were conducted after applying a given “heating history” with axial pullout force and displacements recorded. The work leads to better understanding of soil-pipe interaction mechanisms generating currently scarce data needed for robust and cost-effective designs of DH pipe systems.

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