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 pad on top of a very thick plain concrete block?

Foundation pad on top of a very thick plain concrete block?

Foundation pad on top of a very thick plain concrete block?

I am in a troubled situation.

1) I have to put a foundation pad
2)The pad is subject to some 20tons uplift
3) I have very little room for it and very little soil mass to rely on
4) Dont want to rely on the soil fill below it, cause no guarantee it will be compacted without damage to neighboring structure.

So I dig into the narrow area and fill with plain concrete and later on cast the pad


1) Is the bond between plain concrete and my later-on-added pad reliable againt 22tons ?

2) IF not, will dowels placed in plain concrete be useful?

3) If not, should I specify some SIKA? (I am not very happy with this alternative though)

4) Whatever my experienced friends recommend.

Respects and Regards


RE: Foundation pad on top of a very thick plain concrete block?

Hi IJR...
To get adequate interaction with the plain concrete block and an overlying slab for uplift, you will need a positive connection between the block and the slab.  I would suggest "dowels" but not in the shape or configuration of typical dowels.  I would use deformed bar in a rectangular configuration similar to the ties used for a beam.  Allow this to be cast into the plain concrete with enough exposed to engage the overlying slab.

I would not rely on a "glue" bond for substantial uplift.  If failure occurs it will be fast and unforgiving.  A typical concrete-to-concrete bond without enhancement would likely not be adequate, though I don't know the areas involved.

One thing you might consider is to use helical anchors to enhance both the plain concrete's uplift and the attachment to the overlying slab.  The helical anchor could be placed, the plain concrete placed, and an extension of the helicals allowed to extend through the plain block into the overlying slab.  This ties everything together for good mass resistance as well as soil interaction resistance.

Good luck.


RE: Foundation pad on top of a very thick plain concrete block?


There is another reason that Ron's suggestion of helical piers is excellent.  If you do not trust the native/fill subgrade, some means of carrying/supporting the new construction load, to include the concrete underpad 'ballast' is justified. If you are concerned about the nearby structure, the potential disturbance to the native/fill subgrade must be minimized. The helical should be designed to carry the excess load which the native/fill subgrade may not be able to carry. Depending on the soil profile, the design of the helicals may be controlled by either hold down required or the expected structure weight due to subgrade consolidation.  

This is an interesting problem and would require good soil samples, complete soil consolidation testing and some thought.     Have Fun!

RE: Foundation pad on top of a very thick plain concrete block?

Easter Greetings


Now for the rest who might visit here: My current position allows me to use dowels as explained above by Ron.In the area I am helicals are not yet in the market though there are efforts to bring them in.And definitely no glue bond.



RE: Foundation pad on top of a very thick plain concrete block?


While thinking over your problem, I realized that I got tunnel vision, based on Ron's excellant suggestion of helicals. Not too long ago I had 2 projects which used small diameter (<10" or 25 cm)piles, which could be driven or pushed. Depending on the subsoil conditions, sufficient resistance for uplift could be achieved, along with desirable increased bearing.

As per my previous suggestion, the piling could take a small to large percentage of the load, both support and uplift, making part or all of the extra excavation and concrete ballast unnecessary. Unless very firm bearing is encountered during pile placement, the piles and the subgrade soils will probably be subject to some settlement. A balance is usually made between the amount of settlement (convenience) which can be tolerated and the length/number of piling (expense) to be inserted.  I am afraid that precise numbers will be hard to come by, a condition which is always worrisome for my structural brethren.

But never fear, the Romans used the same technique with wooden piles, some works which lasted for centuries!!

Good subsurface information, laboratory testing (consolidation) and interpretation will be required. My previous, similar projects were interesting and I am sure this will be for you.

RE: Foundation pad on top of a very thick plain concrete block?

Thanks Emmgjld for keeping the faith and revisiting here.
And it so happened that your last comments turned in the right day where my concentration is at a max.

So thanks man


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


Research Report - How Engineers are Using Remote Access
Remote access enables engineers to work from anywhere provided they have an internet connection. We surveyed our audience of engineers, designers and product managers to learn how they use remote access within their organizations. We wanted to know which industries have adopted remote access, which software they are using, and what features matter most. Download Now
eBook - Managing the Context of Product Complexity Using the Digital Twin
Keeping track of changes to complex products is difficult—think Aerospace & Defense equipment, new generations of commercial aircraft, and software-based automobiles. A new way to managing the digital context of the physical product is required and the answer is the Digital Twin. This ebook explores the opportunity available for Operations and Maintenance for the Digital Twin. Download Now
White Paper - Trends in Industrial Filtration
Substantial progress has been made in filtration technologies in recent years. New filter media materials, designs and processes have led to filters that are more efficient, reliable, compact and longer lasting. This white paper will discuss the various trends that are impacting operational responsibilities of MROs today and the resources that are available for staying up-to-date on the latest filtration solutions. 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