Causes of Lateral and Upheaval Buckling
When a pipeline is under operation at a temperature and pressure higher than ambient,
it will try to expand. If the line is not free to expand, the pipe will develop an axial
compressive force. If the force exerted by the pipe on the soil exceeds the vertical
restraint against uplift movement created by the pipe’s weight, its bending stiffness, and
the resistance of the soil cover, the pipe will tend to move upward, and considerable
vertical displacement may occur. The pipeline response may then be unacceptable
because of excessive plastic yield deformation. Upheaval buckling is hence a failure
mode that has to be taken into account in the design of trenched and buried pipelines.
Upheaval Buckling Calculation
The calculation for the upheaval buckling is based on the technical paper “About
Upheaval and Lateral buckling of embedded pipelines” by Dr. K. Peters (3R
International Edition 2006) for the underground pipelines and flowlines.
Based on the calculations, the maximum allowable overbend angle, in 12m of pipe
length (Cold bend length considered in Pipelines), along the pipeline route and other
calculation parameters are specified in the applicable calculation reports and the
drawings. The calculations can also be done with the development of programs in
‘Mathcad,’ or equivalent software based on Dr. K. Peter’s technical paper as mentioned
above.
The calculations model is carried out in 2- phases,
Phase 1: Calculation is done based on the topographically surveyed pipeline corridor
profile
Phase 2: The verification phase for the design model is based on the actual survey for
the top of the pipe in the trench after lowering and before back-filling.
Saipem Classification - General Use