Soilder Pile Design - Spacing 2

[Rakra]

Can someone provide advice on the use of material properties (friction angle, unit weight)of the retained material to determine lateral spacing of soilder piles? The structural engineer in this instance is asking if the material parameters we have provided can be used to determine the maximum lateral spacing of soilder piles.

The wall in this case, is to retain 3-4m high of an excavation face. Materials to be retained include highly to moderately weathered siltstone and soils.
Any examples, sources would be appreciated.

Thanks

 

[JedClampett]

From someone who has never done one of these, but has checked a few, I would say if you gave the at-rest (or active?) soil pressure and the corresponding surcharge pressure, the rest of the design involves structural decisions. the structural engineer needs to decide how far to span the lagging and in turn, how heavy to make the piles.
If I'm the structural engineer, I don't like to get friction angles or any of those internal properties. I'd prefer a simple number (usually pcf), so I don't have to look up in my big soil books how to convert them to the pressure per depth.
I looked in my four references for foundation design and couldn't find one with a good design example. The best I could find was a picture of one in Merritt's "Standard Handbook for Civil Engineers"

 

[PEinc]

Lateral spacing of soldier beams is more dependent on the strength or capacity of other wall components such as tieback anchors, tieback wales, braced wales, lagging, etc. There are many available steel sections for soldier beams but these other factors usually control soldier beam spacing.

http://www.PeirceEngineering.com

 

[PEinc]

Another important consideration when chosing soldier beam spacing is the spacing of any drilled shafts (caissons) that may need to be installed at subgrade after the soldier beam wall is constructed. You should not locate a soldier beam in front of a drilled shaft location or else the shaft excavation could eliminate the passive resistance that supports the soldier beam. For example, if drilled shafts are to be installed at 30' on center along the sheeting line, it would be prudent to install soldier beam at maybe 7.5' or 10' on center.

http://www.PeirceEngineering.com

 

[Rakra]

@ PEinc and JedClampett - Thanks for your feedback, much appreciated......The structural engineer in this instance was trying to get us to confirm if he could use the material properties we had provided in his retaining wall design even though we had supplied the recommended values already in our report. The values were based on experience and literature. I'm beingining to think he was trying to get us to to confirm those values and not only recommend them, to save himself incase anything went wrong.

Also the test program was only test pitting with lab testing only consisting of soil classification tests. The level of investigation was outlined by the structural engineer. This was for a 5 storey building with medium to slightly weathered bedrock at less than 1m depth and on a slope.