HDD S-Curve

[Tauhooyee]

How to calculate stress of HDD construction according to S-curve in the horizontal plan and also curve in the vertical in 1 HDD.
It look like combination radius of horizontal and vertical.
Very appreciate for all answer

 

[LittleInch]

Bending moment.

Results in positive and negative axial stress.

S curve horizontally is not very common.



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[Tauhooyee]

sorry for my poor English language.
This is my problem as the picture to calculate the stress of HDD during pullback.

 

[Tauhooyee]

And this is another location for the problem about the HDD stress calculation during pullback.
We can not construction by another method due to the area limit.

 

[LittleInch]

Can you attach those drawings as well as I can't see enough detail.

What is the bend radii? Horizontal and vertical?

How long?

Has any contractor said they can do this yet?

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[Tauhooyee]

Dear Sir
Already attached file by PDF.
Very appreciate for your responded.

 

[Tauhooyee]

Dear Sir
Another attached file by PDF.
Very appreciate for your responded.

 

[LittleInch]

On your main drawing I see a 1.6km long drill with two 90 degree bends. The second drawing looks like a shorter option?

Bend radius looks OK - about 1400D, but whether this pull back is feasible I really don't know. There will be a LOT of friction on the side wall of the pipe. You really need to get some buy in from a contractor who can do this convoluted drill.

Also your min depth looks very low (about 8m) with a positive head of about 14m from entry point to existing ground level.

I suspect you have a high risk of a blow out there.

Oh and missing another pipe by 1m?? Can't see that happening.

So is your stress question about pull forces and tension or installed elastic bending stresses??

why can't you go straight?
Why so shallow at the mid point?

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[Tauhooyee]

Dear Sir
Yes, my question are the stress calculation for installation and operation.

 

[LittleInch]

well you still use elastic bending moment in your calculation, but axial pull forces in installation are not easy to estimate in this situation due to the bends.

you definitely need some installation contractor advice on that one.

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[KVdA]

R=sqrt((Rh^2*Rv^2)/(Rh^2+Rv^2)) with Rh= horizontal radius and Rv=Vertical radius

 

[Tauhooyee]

Dear All
Very appreciate for all responded.

 

[DDRJHD]

I am curious how you made out with this? These types of horizontal curves are not uncommon in Europe and are a part of the majority of the HDD due to very congested areas. HDD with horizontal curves totaling over 180 degrees with very tight tolerances have been realized on many occasions.

The concern on the provided drawing would be the lack of depth of cover. A crossing of this length we have a great deal of annular pressure and there for will require to be drilled within the correct soil layers with sufficient covert to withstand the pressures created. L