Extracted Grouted Soil Nails - Images needed

[SC4567]

I’m looking for images (or possibly engineers logs) of extracted fully grouted soil nails to assist in understanding the causal mechanisms in a failed soil nail retaining structure forensic investigating I'm involved in. What would help would be images of fully grouted nails preferably pulled rather than exhumed from the slope to make the comparison of what we are observing and what others have found. Can anyone point me in the right direction?

 

[PEinc]

Try contacting the Deep Foundations Institute. It has a tieback and soil nail technical committee.

http://www.dfi.org

http://www.dfi.org/commhome.asp?SOIL#

http://www.PeirceEngineering.com

 

[PEinc]

Try this photo of a recently extracted, 3.5" diameter, low pressure grouted, vertical, test nail. The circumference readings can be divided by 3.14 to get the actual grouted diameters of the bonded length. Soft soil expanded from the weight of the fluid grout causing the bonded length to be a bit larger than the casing pipe OD. This test nail was augered to the depth for the pvc unbounded length. Then the bond length was drilled with the 3.5" casing which was cleaned out with a roller cone bit.

www.PeirceEngineering.com

 

[John2025]

PEinc, Out of idle curiosity, do you remember what kind of force it took to pull that out?

 

[PEinc]

John2025, two anchors were tested to failure. Their bonded lengths were 4.625" diameter by 96" long. One anchor failed at 24.32 kips (17.4 psi bond) and the other failed at 16.22 kips (11.6 psi bond), overall, not too bad for tremie-poured anchors (not pressure-grouted). I think the contractor used his drill to pull the anchors out of the ground. The soil was black silt fill with some glass and brick fragments; therefore, the N values (blow counts) varied a lot.

http://www.PeirceEngineering.com

 

[John2025]

From a guy with zero experience, that's a surprising hold from just gravity filling. Intuitively, you'd think it would take a lot of pressure to adhere that well. Thanks for the real world example.

 

[PEinc]

Various publications show typical bond stresses, or ranges of stresses, for different soils and rock - both for low pressure, tremie grouting and high pressure grouting. Look on-line for FHWA manuals for soil nails and anchors walls. Also PADOT have its Design Manual DM-4 on-line. See Appendix O. Other State DOT's probably have similar manuals. Anyone involved in grouted ground anchors should also buy a copy of the Post-Tensioning Institute's Recommendation for Prestressed Rock and Soil Anchors.

http://www.PeirceEngineering.com