10-02-2012, 01:22 PM

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?

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?