At the European level, the functional requirements for transmission gas pipelines at operating pressures of above 16 bar are governed by EN 1594. For the basic dimensioning, the internal pressure is supposed to be the leading load case (standard load condition). The influence of additional loads and the interaction with the surrounding soil are not taken into consideration in this model. For pipeline sections where significant external loads may be encountered, a more extensive planning has to be performed using established assessment methods.
For some standard load cases of buried pipe systems, there are simplified approaches available to address day-to-day engineering needs, e.g. VdTÜV Instruction Sheet 1063 or Annexes A to F of EN 1594. These standardized methods consider specific aspects, e.g. regarding pipe ovalization, settlements, mining subsidence or frost heave. Comparatively few assessment models are available for holistic investigations of complex and combined load profiles. As one possible approach, EN 1594 specifies numerical simulations in line with the finite element method.
Within the scope of the presented work, a simulation model was developed which completely depicts the buried pipeline and the surrounding soil. The model was validated using a number of analytical methods. The bedding conditions in the pipe trench are described by means of a standardized criterion which takes into account the filled soil type and the degree of compaction. The modular design allows the application of any loads, e.g. earth loads, traffic loads or temperature strains. The result provides a three-dimensional deformation plot of the pipeline and the ground. The extended elastic analysis according to EN 1594 is used as stress criterion for structural integrity assessment. The model can be used to answer specific engineering questions, e.g. in the framework of changed boundary conditions at existing high-pressure gas pipelines or new construction projects.