Alternative soil curves
The bilinear curve is the most commonly used scheme of the R-d curve. Tests have shown that for the friction soil curve the bilinear curve is the best approximation. For the lateral soil curves in general a more gradual relationship is found and the Tanh curve is a good approximation for sand and clay. The Bgc curve can be used for peat soil materials.
An option is to apply a slack around the pipe, for instance in case of a surrounding jacket tube or may be in a fresh bentonite bore hole.
The slack values may vary in the same three main directions, upward, downward and sideward. Slack values in directions in between are deduced from the values in the main directions by means of elliptic curves. The friction becomes active as soon as the pipe has displaced over the lateral slack.
PipelineSoilCurves, last changed: 1/31/2020