To determine behavior of critical temperature which results in longitudinal expansion of the pipeline, which might cause upheaval buckling and failure.
FE software is used to model the pipe and to determine its buckling characteristic. To assess pipeline stability against the UHB, the uplift resistance of the soil is typically used as an input for mathematical modeling to determine a safe burial depth (H/D).
A pipe with an initial imperfection buried in dense sand is focused. An analysis is done for the buried pipes considering different values (0-50 %) of post peak reduction of uplift soil resistance. A two noded, two dimensional linear beam element is used for modeling the pipe while the soil is modeled as nonlinear springs in both axial and vertical directions. An element size of 0.5 m is used for the pipe after mesh conversion. It is assumed that pipeline can not move in downward due to rigid seabed, high spring stiffness is used in the downward direction.
Conclusion:
Thermal expansion of buried pipelines may cause upheaval buckling if the uplift resistance offered by the backfill soil is not sufficient to prevent upward displacement.
For the given pipe diameter (D), as the soil cover (H) above the pipe increases with H/D ratio, the uplift resistance (Fv) of the pipe also increases and therefore, higher critical temperature is required for the Upheaval buckling (UHB) of pipe.
