Soil Nail Wall v Tieback Wall

[laxplyr]

This maybe too basic of a question, but...

Whats the basic difference between these two wall systems? They sound similar... is it shotcrete face v facing elements???

 

[Focht3]

Tie-back wall usually has a structural wall (reinforced concrete) that distributesthe tie-back forces; soil nail wall doesn't have much (no?) "face" load, so the exposed surface can be shotcreted.

 

[PEinc]

The difference is in soil nails vs. tieback anchors. Soil nails are usually shorter with much lower lower design loads than tieback anchors. In length, soil nails usually are between 70% AND 100% x the wall height. Grouted tieback anchors are usually longer than 30 feet with 40 to 60 feet being more normal for most applications. Sometimes, tieback anchors are much, much longer than 60 feet. Soil nails are usually installed at closer spacings than tiebacks. Nails may be installed at an area of approximately 25 SF per nail (5' x 5') while tiebacks may be installed at an area of approximately 120 SF per nail (sometimes more, sometimes less). Tiebacks are active support members. They push on the retained soil harder than the earth and surcharge pressures would push on the wall. Soil nails are passive support members. They provide their support as the soil mass begins to mobilize. Both soil nails and tieback anchors might have similar corrosion protection details. Every tieback anchor is usually proof or performance tested. Most soil nails are not tested. Usually a small percentage of the nails are tested or non-production nails are tested.

Soil nail tendons are usually Grade 60 or 75 threadbar tendons. Tieback tendons are usually either threadbar tendons (Grade 60 to Grade 160) or multi-strand tendons (Grade 270).

Soil nail walls are soldier beamless walls. Shotcrete and nails are the support. There may be a second or permanent facing of shotcrete or even a precast facing attached to the nails. Tiedback walls often use soldier beams, lagging, and tiebacks with a precast or cast in place concrete permanent facing when required.

Soil nail walls become economical when the retained soils have a little cohesion and when it may be expensive to install soldier beams. Uncontrolled ground water can be a big problem when constructing either tiedback or soil nail walls.

Both tiedback and soil nail walls are meant to be constructed from the top down, in a cut situation. If your wall is a fill or embankment wall, anchored walls are usually not the best wall type. Try an MSE wall or conventional concrete wall.

This was just a few quick differences. There are others.