Bitumen Coated RC Precast Pile to Reduce Dragdown 3

[struggle67]

Hi

Is bitumen-coating on precast RC pile to reduce drag-down common? Is it efficient and reliable? What should be the percent reduction in negative skin friction? Is there any code or reference that I can refer to for my calculation and material specification?

Thanks

 

[EireChch]

IMO - Not very common at all. I think its an old school method of reducing down drag that wouldn't be permitted for environmental reasons nowadays

Just design to allow for downdrag.

It is a subject that is gravely mis understood.

Many people determine the magnitude of drag load and minus it from the allowable capacity. It has nothing to do with geotechnical capacity. It only affects structural capacity and settlement. That is of course if you believe Fellenius.

 

[dik]

Many bitumen coatings are carcinogenic. On any of my projects, I require the EOR to confirm that they aren't.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[struggle67]

Thanks, Guys,

It only affects structural capacity and settlement. That is of course if you believe Fellenius.

I am quite new to this but I think I can imagine skin friction being negative during consolidation and then back to positive after drag down / settlement. In my case, settlement will be quite a lot to allow for.

 

[HTURKAK]

As far as i know, It is not common . Bitumen coating is applied above the neutral plane and can reduce the skin friction by ≥ 50 %..The thickness of soft bitumen coat should be in the range of 10 mm.

For reference , you may look ;

-Pile Design and Construction Practice ( by Tomlinson)

- Pile Deisgn for structural and geotechnical engineers( by Ruwan Rajapakse )

I would prefer to design for down-drag ..

 

[Retrograde]

Bitumen coatings can also cause issues with pile driveability.

Chapman G.A., Seidel J.P., Wagstaff J. (1991) The Effect of Bitumen Slip Coating on the Driveability of Precast Concrete Piles. 4th Intl. Conf. on Piling and Deep Foundations Institute, Stresa, Italy, April, 1991, Vol. 1 : 193-199.

 

[EireChch]

The magnitude or settlement is irrelevant, whether its 2mm or 2000mm the magnitude of drag load remains the same.

Check Fellenus 247 publication on the topic.