×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Soil Nail Wall Wall, Exteral Force Required...

Soil Nail Wall Wall, Exteral Force Required...

Soil Nail Wall Wall, Exteral Force Required...

(OP)
I have to build a permanent soil nail wall 6m high to retain soil sloping at an angle of 15 degrees from the top of the wall back.

I have analysed the wall using GeoSlope software SlopeW and have come up with a solution which gives an adequate FoS.

However, the soil nail anchors used encroach on a neighbouring property which is 2.8m from the retaining wall, and so i need to calculate the external force required to make the section stable. I have been told to treat the modelled section as a high strength soil.

How do i go about calculating the external force required?

I'm only new in the field of geotech and would appreciate any help or guidance.

thanks.

RE: Soil Nail Wall Wall, Exteral Force Required...

2.8m long nails are too short for a 6m high wall, especially with an upward sloping ground surface behind the top of wall.  2.8 / 6 = 0.466H. Tieback anchors would be even longer than the 2.8m long nails.  Even at a 20 degree angle, the maximum nail length would be about 2.98m or 0.496H, still too short.

Pick a new type of (more expensive) wall or get permanent soil nail easements into the neighbor's property.

www.PeirceEngineering.com

RE: Soil Nail Wall Wall, Exteral Force Required...

I've done a similar wall with helical tiebacks at 45 degrees to get helices at least 5' beyond failure plane.  Keep top tier at least 5' down here.  Deeper toe for soldier beams needed due to vertical component of ties.  Double up ties at each point to keep individual tie loads down if needed.

RE: Soil Nail Wall Wall, Exteral Force Required...

PSlem, this is a soil nail wall, not a tiedback wall.  A top nail needs to be closer to the surface than 5'.

www.PeirceEngineering.com

RE: Soil Nail Wall Wall, Exteral Force Required...

Right, but soil nail won't work so I picked "a new type of wall"

RE: Soil Nail Wall Wall, Exteral Force Required...

The "Snailz" program, available free from Caltrans's website, has an option to 'apply external force' to a soil nail wall. Adjust the (user-input) force until the desired factor of safety is achieved.

[An upper limit of the force should be <=(FS)x(ka)x(gamma)x(H^2)/2, because the soil mass mobilized by the nails provides partial stability.]

...and then the physical device for applying this force will need to be designed and incorporated into the construction.

RE: Soil Nail Wall Wall, Exteral Force Required...

If there is not enough room to install long enough nails or tieback anchors, how would an external force be provided and evenly distributed over the soil nail wall facing?

If an external force is provided, it would be important to check the intermediate construction stages to make sure the wall is stable as it is being built.  It is not wise to just add a lot of force (or a much longer nail) at one location and then believe that the wall is stable.  For example, an extra long bottom nail will raise the calculated safety factor on paper but, in reality, may not stabilize the upper portion of the wall.

www.PeirceEngineering.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources