Rectangular or Staggered Soil Nail Grid Pattern?

[Obregon]

Hello. As far as I know, installing soil nails/ground anchors in a staggered grid pattern has advantages regarding load distribution along the facing. Nevertheless, the process can become more time consuming, particularly in slope stabilization as opossed to top-down wall construction.

Do you have any design/construction experiences on selecting one method or the other? Thank you.

 

[PEinc]

Staggered or aligned? This usually does not matter to me unless there is something behind the wall (piles, utility, drilled shaft, etc.) that I don't want to hit with nail drilling or want to drill too close to.

http://www.PeirceEngineering.com

 

[Obregon]

Hello PEinc, thank you. According to some serious sources "Horizontal rows of soil nails should be staggered to improve the integral action between the soil nails and the ground." (Guide to Soil Nail Design and Construction - Hong Kong Geotechnical Engineering Office 2008).

"Soil nails are installed on the excavation face in “square” or, more commonly, “staggered” (also referred to as triangular or offset) patterns"; "A staggered pattern results in more uniform earth-pressure distributions, better soil arching effects, and provides a slightly larger resistance compared to those from a square pattern." (Soil Nail Walls Reference Manual - FHWA 2015).

I wonder how important and under which circumstances these recommendations should be followed.

 

[EngMan40]

Obregon, It is not too important unless you have something behind the wall you're trying to avoid as PEinc indicted. This is just academics and if you properly design the wall it will be just fine and dandy.