Floating Slab on Deep Foundations with High Water Table
Floating Slab on Deep Foundations with High Water Table
(OP)
Hello:
I am wondering if anyone has come across this condition before. We are looking at a building with a basement which is located in an area with a very high water table. Therefore we need to use a mat foundation which we can waterproof around it and use its weight to resist the buoyancy forces.
The problem is that the soil engineer has indicated that the soil under the basement is not suitable for bearing. He is suggesting that we use piles. The problem is, how do we waterproof the locations that we will have to penetrate the mat for the piles to go down?
Has anyone encountered a similar situation? How have you resolved it?
Thanks,
Craig
I am wondering if anyone has come across this condition before. We are looking at a building with a basement which is located in an area with a very high water table. Therefore we need to use a mat foundation which we can waterproof around it and use its weight to resist the buoyancy forces.
The problem is that the soil engineer has indicated that the soil under the basement is not suitable for bearing. He is suggesting that we use piles. The problem is, how do we waterproof the locations that we will have to penetrate the mat for the piles to go down?
Has anyone encountered a similar situation? How have you resolved it?
Thanks,
Craig






RE: Floating Slab on Deep Foundations with High Water Table
Typically, the piles are driven before the mat is constructed. The piles should provide bearing for the whole structure and the primary resistance to buoyancy. Thus, you may not need the mat for buoyancy resistance. However, you may still need a mat for settlement reasons, but it will likely not need to be as thick.
Talk with your geotech and a senior structural engineer for more information.
Jeff
Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com
RE: Floating Slab on Deep Foundations with High Water Table
I understand the engineering princpals. However, I am more concerned about the waterproofing. The basement not only will act but has to act like a boat so we don't get water into it. The piles seems to be a conduit for water to infiltrate the structure.
If we were to use just a mat we could waterproof around that and up the walls.
Craig
RE: Floating Slab on Deep Foundations with High Water Table
RE: Floating Slab on Deep Foundations with High Water Table
RE: Floating Slab on Deep Foundations with High Water Table
In my opinion, the best waterproofing for walls and construction joints, is bentonite. One trade name is Volclay at this link
http:/
For waterstop, there are also bentonite based products such as this
http://www
Best Wishes
www.SlideRuleEra.net
RE: Floating Slab on Deep Foundations with High Water Table
Hydrophillics, as recommended by SlideRuleEra are very good and might help prevent much water ingress. Generally, where work is below water table, it is sensible to provide a method of positive drainage within the basement. I've previously specified GRACE cavity drain products for this but there are many similar systems.
Outside the drained cavity it is usually acceptible to rely on the concrete with water bars or hydrophillics at the joints as there is no need to totally eliminate any possible ingress.
RE: Floating Slab on Deep Foundations with High Water Table