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


Foundation settlement

Foundation settlement

Foundation settlement

I have an existing structure (3-story) 1 to 2 meters from a retaining structure, Soldier pile (5.2 meter excavating)with tieback. The soil profile behind the retaining structure is loose clayey sandy soil (layer thickness 1.5 to 2.5 meter) overlying on soft to medium stiff lean clay, water table is about 1.75 to 2 meter from ground surface. The structure foundation start showing settlement (3.8 cm) when the contractor start dewatering. there is no deflection in the retaining structure.

Anyone with experience on this condition?

RE: Foundation settlement

You really did not give enough information to identify THE cause of settlement. Your excavation is close enough to the existing structure that underpinning may have been a better way to support the structure. 3.8 cm is more than should be expected with proper underpinning. Sheeting deflections could have caused the settlement. However, dewatering may also have caused the settlement. Dewatering makes the soil heavier which can cause the "loose clayey sandy soil" to consolidate and settle the building.


RE: Foundation settlement

there is no deflection in the sheeting. I thought that the lean clay is expansive soil which cause the settlement.

RE: Foundation settlement

Expansive soil would cause heave, not settlement. Moisture would have to be introduced into the expansive clay to cause heave. With groundwater above the clay, it is not likely that you'd see 3.8cm of heave over the course of a short duration, especially if you are dewatering.

Was the shoring wall surveyed near to top of the wall and prior to excavating? I've seen some contractors survey after they have excavated which does not tell you how much the wall initially deflected. Also the location of the survey points are important. Typically movements are greatest at the top of the wall than the bottom. Theoretically this could be wrong depending on where the tiebacks are installed.

I agree with PEinc. Due to the walls close proximity of the building, underpinning would have been a good idea. De-watering could be causing consolidation of the soil underneath the building.

RE: Foundation settlement

Dewtering is a common cause of settlement, since the formerly submerged soil now is not affected by buoyancy and weighs more..

RE: Foundation settlement

A sketch x-section showing the existing building and the anchored wall would be very helpful. Is 5.2m excavation depth close to the building?

RE: Foundation settlement

"I have an existing structure (3-story) 1 to 2 meters from a retaining structure, Soldier pile (5.2 meter excavating)with tieback."


RE: Foundation settlement

tk78 Your statement.
"I thought that the lean clay is expansive soil which cause the settlement."

Lean clay normally is not expansive and more likely is compressing as it goes from saturated below the water table to above a water table. Don't blame settlement on the retaining structure. Get an experienced geotch on the job before you cause more damage.

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!


White Paper – Your Construction ERP RFP Checklist
Selecting business software for a medium to enterprise-sized construction concern is extremely challenging in large part because most enterprise resource planning (ERP) suites originated in the world of repetitive manufacturing and are therefore a poor fit for a project and asset-centric business. However, midsize to large contractors need the predictable, auditable processes that ERP delivers. 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