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Soil settlement and pipeline displacement - Printable Version

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Soil settlement and pipeline displacement - peipei - 10-02-2012

Dear Mr./Mrs.
I am now calculating the maximum settlement value for specific pipes. The assumption is simple, a straight pipe with infinite open model boundary, in the middle of the pipe, there is a double shape settlement loading. The aim is to find the maximum tolerant value.
[attachment=217]
Background
According to paragraph 4.5 in the “theoretical manual” published in 1989 march, version 3.02, the resulting soil reaction will be where
- K represents the soil stiffness
- ∆S is the movement of the soil, input SUBZMAX in function 4.2
- ∆P is the distance with which the pipeline move together with the soil movement, output U-Z in function 5
And there will be two cases,
- the pipe follows the soil settlement completely, ∆P=∆S, then U-Z=SUBZMAX
- the pipe is rigid, ∆P<∆S, then U-Z<SUBZMAX
Example
Pipe: DN800 water pipe with a wall thickness 9.52mm
Loading: pressure 5 bar and the settlement (-44mm, uncertainty factor 2)
From the calculation results, the input subsidence length has a large influence to the stress, see pictures below, the blue colour is SUBZMAX and the pink colour is U-Z.
[attachment=223]
[attachment=224]
[attachment=225]
//pictures resized by moderator//
Questions
- In the third case with a 24 m length, why the U-Z could be larger than the SUBZMAX? The pipe could either completely follow the soil or rigid enough move less than de soil. What is the physical meaning if ∆P>∆S?
- If the input length follows NEN-3650, in this case, would be 20 m. Then the maximum settlement is larger than case 1 and case 2, which will show the similar shape as the length is 24 m. How could you determine an optimum length for specific pipe?


RE: Soil settlement and pipeline displacement - ir. M. Lammers - 16-02-2012

(10-02-2012, 01:22 PM)peipei Wrote: Questions
- In the third case with a 24 m length, why the U-Z could be larger than the SUBZMAX? The pipe could either completely follow the soil or rigid enough move less than de soil. What is the physical meaning if ∆P>∆S?

Regarding your first question:
You should draw the applied settlement loads (SETLZ*F). These loads can be found in Function 5 (pipeline behaviour) under additional output tables: S-LOAD or 'Applied settlement loads'.