Pipeline Parallel under Road Pavements
Is there any guidance available for running a pipeline parallel to the edge of the road and under road pavement?
AS2885.1-2018 provides some guidance in Figure 5.8.8(B) for appropriate minimum spacing for external threats but a question has been raised of how to deal with the vehicle loading.
The initial assumption is to utilise API 1102 however there seems to be some statements in that standard (and perhaps interpretation issues of if running parallel to the road is a “0 degree crossing”) which is throwing some confusion into its applicability as it’s “less than 30 degrees”. There is also another statement in API 1102 Cl 126.96.36.199.2 which suggests the calculations performed for the typical 90 degree road crossing results in the highest pipeline stresses, which one would therefore assume if a 90 degree crossing calculation passes, a parallel pipeline would also pass.
(James Czornohalan/ Peter Tuft)
Pipelines running parallel under roadways can be treated in the same way as those crossing perpendicular. As the question correctly notes, a 90 degree crossing is the worst case scenario so using a 90 degree design for other angles will produce a conservative result.
However, it is important that this is properly considered in the safety management study.
On the issue of API RP 1102, AS 2885 mandates that the pipe at any road crossing will have a total combined stress of not more than 90% of the SMYS. It does not mandate the use of API RP1102 in it's entirety. API RP 1102 is suggested as a calculation method, but it is the responsiblity of the designer to understand it's limitations before using it. It may be that an alternative method of calculating the stress in the pipe is required in this case.