Soil Nail Wall Deformation

[NS4U]

See page 95 (PDF page 117) of the file at the following link.

http://isddc.dot.gov/OLPFiles/FHWA/010946.pdf

It relates to the design of soil nail walls, Figure 5.18 (b) essentially says that the nail “head” will move inward (ie into the soil) at ultimate load. This is opposite to the direction of the applied force.

This does not make sense to me. At ultimate I would expect that the soil nail (which is in tension) elongate and move outward.

Can someone explain what is going here?

Thanks

 

[PEinc]

The nail head does not move (except due to some elongation of the nail tendon). The shorcrete wall facing will try to push forward as the earth pressure builds up when additional excavation is performed in front of the wall. Since the nail head remains relatively in the same location, it only appears that the nail head is moving inward. You will not notice this happen unless your nails are too far apart and you greatly underdesign the shotcrete which then starts bulging between nails.

 

[JedClampett]

I think the wall moves out and the soil nail stays where it is.

 

[NS4U]

I agree 100%, but the from the Figure, there is an "initital position" line and it clearly shows the nail head moving away from it... in the direction opposite to the load none the less

 

[JedClampett]

well, the figure is wrong.

 

[NS4U]

Seems like a pretty big mistake, not to mention a similar thing is shown in Figure 5.20.

So I find it hard to believe that the figure is incorrect

 

[NS4U]

Sorry, I mean... I find it hard to believe that the figure is correct

 

[BAretired]

NS4U,

I think you are absolutely right. The initial position should be moved to the right on Fig. 518 (b). There is also a mistake on Fig. 518 (a). The arrow pointing to the circle around the nail should be labeled "Fracture on internal face".

Looks like a slip in editing the document.

Best regards,

BA