×
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

Lateral Pressure Coefficient k0 for compacted soils

Lateral Pressure Coefficient k0 for compacted soils

Lateral Pressure Coefficient k0 for compacted soils

(OP)
Hi,

What is the recommended method to estimate the lateral pressure coefficient k0 for compacted soils (for a culvert design)?

I am aware of the k0=1-sin(ϕ)×OCRsin(ϕ) equation, but I'm not really sure how one would estimate the over consolidation ratio for a compacted soil. Is there a specified proctor compaction percentage to OCR relationship? Alternatively, are there any good rules of thumb (preferably with a reference).

So far, the best I've found is the commentary on AASHTO LRFD 3.11.5.2, which states that the lateral pressure coefficient for lightly overconsolidated sands is somewhere between 0.4-0.6 and, for heavily overconsolidated soils, the k0 may be around 1.0. No idea where a compacted soil would fit on that scale.

For the record, for my particular application a higher k0 is preferable, so I'm trying to identify what's the maximum k0 I can reliably obtain if the fill is compacted essentially against the wall.

RE: Lateral Pressure Coefficient k0 for compacted soils

When you see the leaning wall that supports a fill which was compacted by a roller running alongside it, the K value is pretty darn high, certainly not 1.0. Successive passes on the fills sequential layers add to the pressure on those below. I measured increases in wall pressure 8 feet below as a roller passed along above.

RE: Lateral Pressure Coefficient k0 for compacted soils

Here is a copy of the data for a clean sand backfill and fill height was up to 30 feet. By this you can see the equivalent fluid for compactors at the wall was 75 pcf. That's less than 1.0. Also shown is the effect of moving the compactors out at last 3 feet from the wall. Wall was part of a parking garage and assumed to stay and not move.


That pressure scale is equivalent fluid unit weight.


RE: Lateral Pressure Coefficient k0 for compacted soils

As to culverts and lateral pressure that value (such as 1.0) hasn't come up in my experience. However, as to vertical load and pressure, we usually call that the critical load situation. Allowing for effect of trench side effects and the spreading of that vertical load to the sides of trench, the vertical pressure usually is taken as not more than about 3 times the trench width as vertical fill height. It all depends on the details of the job. Of course for shallow fill over the pipe, surface loads also need to be considered. Test loads on pipe are vertical usually.
Edit add: I should add another situation, rather than a tench. That is an area fill, as a highway embankment. In that case there could be loads from the embankment to the surface. Then the lateral pressure might be simiar to the vertical under some circumstances. Should this situation somehow be providing too high a load on the pipe, consider the "imperfect trench" method of keeping that load tolerable. A Google search might not bring up the method, since it was developed in Iowa maybe 80 years or more back. Spangler was the engineer.

RE: Lateral Pressure Coefficient k0 for compacted soils

See two references for effective lateral pressures on existing (newly placed) walls on backfill operations:
1. Terzaghi, Peck & Mesri. Page 344.
2. NAVFAC 7.2-77.
The wall can "feel" near passive pressures.
You can definitely lean a wall over during backfilling. As well as crack a new concrete wall (I've seen it).
Use thinner lifts and smaller equipment near the wall face.

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


Resources

White Paper – Choosing the Right Spring Loaded Connector
In today’s cost-sensitive world, designers are often driven to specify the lowest cost solution for every aspect of their designs to ensure that their solution is competitively priced and their company remains profitable. However, specifying a low-cost, low-quality connector solution can result in premature failure, considerable re-work costs and damage to reputations. Download Now
eBook – Own the Lifecycle: Sustainable Business Transformation
Increasingly, product and services companies are seeking more information and control in the operational lifecycle of their products, including service and use. Better information about the operational lifecycle, and the ability to use that information, requires more than just unstructured data flowing back from products in the field. Download Now

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