AutoPIPE supports evaluation of buried pipes for upheaval buckling. When buried pipelines are initially deformed due to manufactured overbends, they are subject to upheaval buckling when axial compressive forces are applied. Upheaval buckling can be significant enough to expose previously buried pipes, exposing them to damage from external elements.
Buckling analysis is performed on any point in the model, however this approach requires an initial vertical overbend, defined through the coordinate geometry of the buried pipeline system. In other words, buckling will only occur at points where compressive forces push the pipe upward. Thermal and pressure loading causes these points to push upward and buckle. Should this overbend result in a vertical deflection, the Soil output report will provide additional soil depth required to prevent vertical deflection. The Soil output report will then provide soil depth to be removed. For example, if the current soil depth is 60 inches, and the Soil output report recommends 6 inches, increasing the soil depth to 66 inches is expected to reduce upheaval buckling to the allowed vertical deflection.
AutoPIPE uses the following theory by K. Peters.
only considers buckling due to vertical loads, not lateral loads.
The height solution calculated by this method of upheaval buckling may not be applicable to the selected calculation method based on limits of certain properties. For example, Ncv has a limit that (H/D) does not exceed a value of 10, so if the recommended soil depth is greater than 10*D, the program will not allow this soil depth to be used properly.
See "Upheaval Buckling Technology Preview" user documentation in AutoPIPE help (as shown below).