Shore Approach Pipeline design (stability analysis) 2

[judeotuks]

I am carrying our a shore approach design for a 20in gas line. The pipeline will be trenched and backfilled (1 m cover) with sand.

Please I am looking for calculation methods/go-by for assessing the stability of the pipeline/backfill against hydrodynamic forces.

 

[BigInch]

You should bury it to at least 10 feet clear cover in the shoaling area until you reach the block valve. You do not allow water to contact the pipeline in shoaling areas, so there is no stability analysis required. You make sure that the cover material will not be washed away by covering that with mattresses or armor as needed. It is a maximum current and scour analysis that you need, no more than that.

Independent events are seldomly independent.

 

[LittleInch]

There is not much in the way of calculations, more assessment of the backfill, tidal current, waves, especially storm waves to judge what protection may be needed. I assume you have concrete coated pipe, but 1m is quite a low depth unless you have very benign conditions. The risk of trench washout due to wave action, storms etc is high. Rock armour is common and at least 2m cover normal practice from 5m below LAT top above the high water mark.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[cvg]

without knowing the conditions of your site, it is silly to quote numbers like 1 meter, 10 feet or 2 meters of cover over the pipe as being suitable. OP needs to hire an engineer specializing in coastal hydraulics to determine the requirements based on the specific conditions of his pipeline and his shoreline. I suggest taking a look at the USACE shore protection manual

 

[judeotuks]

Oh yes i will have a look at the USACE shore protection manual.
Thanks a lot guys.