Stress analysis of steel pipe installation in horizontal directional drilling based on strain monitoring

Horizontal directional drilling (HDD) technology is becoming a popular method for steel pipeline construction and replacement in oil and gas industry. There is a combination of axial and circumferential stresses and strains imposed on the product pipe during HDD installations. Limited research has been done to analyze the stresses and strains on the steel pipe during installation. A more detailed investigation is required to evaluate the stresses and strains developed during installation to ensure the structural safety of pipelines while identifying areas for design improvement. This paper discusses a strain monitoring program which was utilized in two major HDD installations, including 762 mm O.D. steel pipe in crossings over a kilometer. The strain measurements were presented in the form of pipe strains along the drill path over time for installation. Stress–strain relationships for pipe installation were developed and installation stresses were calculated using the strain measurements. Then, the calculated stresses from strain data were compared with expected theoretical values determined based on current design practice as developed by Pipeline Research Council International (PRCI). High variations in recorded strains and stresses imposed on the pipe were observed in both case studies. The strain monitoring and stress calculation discussed in this paper provides some details on the expected behavior of steel pipes during HDD installations.