Spectrum Pipelines-Upheaval Buckling is used to perform upheaval buckling assessment of trenched and buried pipelines in accordance with DNVGL-RP-F110. Assessment of soil is performed as a first step to establish if it is suitable to mitigate upheaval buckling. Undrained Global and Local Failure checks are performed to establish if the soil could be used as a backfill.
If the soil is very weak clay (low undrained shear strength), deep seated failure may be an issue. This results in local soil failure in which case clay flows around the pipeline resulting in pipe slowly moving upwards and getting exposed eventually.
In such cases soil can not be used as backfill and must be educted out of the trench. However, post eduction some soil slurry still remains in the trench. The software calculates rock cover height required to mitigate UHB for various slurry layer depths.
If soil alone is enough to mitigate upheaval buckling, the minimum depth of soil cover is recommended. However, if soil alone is not sufficient to mitigate UHB, a combination of rock cover over soil backfill is calculated for each Out of Straightness (OOS) height.
The software performs the soft foundation check (i.e. potential for downward failure) in which case it recommends the additional rock cover required to mitigate soft foundation failures.