Grouting of Prestressed Rock Anchors

[s0hail]

Regarding the installation of SSL type Rock Anchors (17m length) in which steel strands coated with grease and plastic coating as corrosion protection my question is could the Rock anchor be grouted up to full length before tensioning? Considering the fact that if Anchors are tensioned after grouting, the grout will most probably be damaged as it would be quite difficult to centralize each and every strand in its position otherwise during tensioning they would align themselves and damage the grout. Does tensioning after grout reduces the capacity of anchor even if steel strands are coated with grease and free to move inside plastic pipe (though the grout is in contact with anchor body and monolithic throughout anchor length)? It is to be reminded that Rock Anchors are designed for 100 years period and as per PTI recommendations severe economical loss is expected on their failure. Is there any guidelines related to grout loss for Rock Anchors? How much grout loss is allowable?

 

[PEinc]

The strands within an anchor have spacers and centralizers at a regular spacing per PTI and the manufacturer's recommendations. The strands are stiffer and straighter than you might imagine. Because the strands are greased and sheathed in their unbonded length, the entire anchor can be tremie-grouted at one time. No reduction in capacity is assumed.
For permanent, fully encapsulated anchors, you will need to grout within and outside of the corrugated sheath. Talk to the contractor or the tendon supplier for more information on this. It's too much discussion to be typed in this forum.

http://www.PeirceEngineering.com

 

[dBasement]

Be really careful though that there is not any intended elasticity for the anchors. I have seen marine applications (dolphins specifically) where stressing the bolt is intended to provide some elasticity. In that case, grout would defeat that purpose.

 

[s0hail]

Thank you for guidance.