Contact US

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!

*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

Installation of geogrid on an incline

Installation of geogrid on an incline

Installation of geogrid on an incline

This may seem like an off-the-wall question but I'm going to ask in hopes of getting a few opinions.

Long story short I have a project that involves modifying an existing embankment slope that was constructed over very soft clay (Su values in the 100-150 psf range). The embankment modification includes flattening the sideslopes to go from an existing 1.5:1 slope to a 2:1 slope. The issue we're running into is that the underlying clay material is too soft to support the wedge of soil we plan to add to the embankment. Our slope stability models predict a very shallow slope failure will occur. The slip plane roughly parallels along the top of the existing slope, penetrates a short distance down into the clay layer, and then exits out of the clay layer 5' to 10' beyond the toe of slope.

We've considered using geogrid in an effort to improve the factor of safety against sloughing/sliding. In the past I've always seen geogrid placed in a series of horizontal layers. However, doing so would require excavating a good portion of the embankment. After thinking about this a bit I'm wondering if placing a few layers of geogrid parallel to the top of the existing side slope would work just as well. The geogrid could be anchored at the top of the embankment beneath the roadway fill and then laid out along the surface of the existing side slope. The proposed fill could then be added over these geogrid layers. I'm thinking we'd also want to loop the geogrid a short distance back into each fill layer to create a reinforced "bulb" of soil at the base of the embankment. In this way the geogrid layers would act as tension elements to resist slippage of the slope and the soil "bulbs" cold help support the slope above. I recognize this may be an unconventional arrangement but it seems logical to me from a load path perspective.

Does anyone have any thoughts on such an installation? Even better, does anyone have any references or case studies for such an installation?

RE: Installation of geogrid on an incline

How high is the embankment? 2H:1V still seems a bit steep for a clay foundation which has been noted. Do you have room for stabilizing berms? That's how we would usually handle such low shear strength clay.

RE: Installation of geogrid on an incline

The embankment is about 15' high and is along a river so we're trying to minimize in-water impact. We've also looked at 3:1 and 4:1 side slopes and, while the FOS for those options are are better, they still don't yield an acceptable FOS of 1.3. A toe berm could be constructed and would certainly help. However, it would require placing fill in the river.

The desire to minimize in-water work is causing us to evaluate this slope reinforcement option.

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! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close