Sliding in Underpinning Design

[Ben29]

How do you prevent sliding in your underpinning design prior to the installation of the new slab on grade?

I have an existing end-unit rowhouse. Two-story, wood framed structure with an existing crawlspace. The first floor wood joists bear on brick stem walls. We dug test pits, and I present to you, our scenario:

 

[PEinc]

Ben29, what you show in your sketch is not underpinning. Also, with 9' of unbalanced earth pressure, a light weight building, and thin "underpinning," you have a significant sliding problem. You will probably need to use some type of lower capacity ground anchors, such as Manta Ray or Sting Ray anchors. Even if you install thicker, normal-type, underpinning piers, I would expect you to have a sliding problem.

Where are you in Pennsylvania?

https://www.williamsform.com/soil/manta-ray-anchors/

https://ii-supplies.com/74-sting-ray-earth-anchors

http://www.PeirceEngineering.com

 

[Ben29]

PEinc: Thank you for your response. I am in York County.

 

[milkshakelake]

There is not only a sliding force problem here, but also an overturning problem. You have walls acting as retaining walls.

I can't actually understand what you're trying to do here, so you have to be more specific. But generally, I'd detail a construction sequence with underpinning and temporary braces to resist the lateral force. I saw your other post about this and I'm replying to an older post, but this doesn't work. Don't remove 1st floor joists before installing underpinning. And the amount of underpinning is huge. You're setting yourself up for a lot of liability by excavating that deep. I don't do it.

Edit: It sounds like you don't have a basic idea about how underpinning works. No judgment here, because I've been in your situation before, but I suggest that you read up about it.