Water pressure on concrete basement wall 1

[gasma1975]

Hi,

Is there a mathematical relation between the flow/current of a river and the pressure against a wall. I have to design a new foundation for a house that was dammaged last year by the flooding, flooding is happening each year in that region, but last year it was very bad. Last year the river had such a current that the (unreinforced concrete wall) did not resist. So I'm trying to figure out what kind of pressure are we dealing with. Any idea ?

 

[Splitrings]

AASHTO has a procedure for calculating stream flow forces on bridge piers. It might be a starting point.

 

[msquared48]

Was it the concrete that failed, or the foundation failing due to scour?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Lutfi]

Why in the world are you trying to design a structure on a river bank against river currents? That defies common sense. I would be worried about soil washing under the footings and walls.

There are many concerns that must be dealt with when it comes to flooding and constructing on water. You have move than pressure to deal with. If you must build by a river, hire a competent person. You may need pilings under the structure to keep it from washing out, again.


Regards,
Lutfi

 

[gasma1975]

The concrete wall failed due to pressure, a big crack appeared and once the water entered, it ripped the wall.

Why I'm designing the wall in such a region ? Believe it or not, but last year more than 4000 homes were damaged. And the canadian (Québec) governement, I guess to keep the voters, decided to pay (with our taxes) to rebuilt the foundation of the houses, first we need to make the foundation higher than the 100 year flood level, and to make sure that adequate reinforcement is present.

But still I do agree that is pretty dumb to rebuild in that region...

 

[msquared48]

Reinforce the walls, use knockout panels, and use a either a deep mat footing, or piling as Lutfi suggested. Consider installing upstream bollards to either hold and/or divert some of the flood debris too.

You may well also get a Geotech involved here.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JedClampett]

The velocity pressure of moving water is not too significant until you get over about 8 ft. per second. That's about one foot of head pressure using v^2/2g. And 8 feet per second is really cooking. I design a lot of water retaining and channeling structures and don't take into account velocity.
It's more likely that the static pressure failed the wall. Usually homes are built in the flood plain (slow rising, slow moving), not in the path of the river.

 

[cvg]

recommend the following references which may help in your understanding of the issues and potential solutions. One solution might be to construct a floodwall between the structures and the floodplain which would handle the water and then reconstruct the structures outside of the floodplain.

• Engineering Principles and Practices for Retrofitting Floodprone Structures, FEMA 259, 2001

• Homeowner's Guide to Retrofitting, Six Ways to Protect Your Home From Flooding, FEMA P312, 2009

 

[MiketheEngineer]

MOVE!!!!

 

[msquared48]

In the Snohomish Valley (I live on the south rim of the valley), the county has instituted re-zoning to eliminate construction in various areas of the floodplain to try to limit occurrences such as this.

So, moving? This should be a definite reality, not just a pipedream.

FEMA has a limited budget for this, plus is slow to respond to the disasters as we are well aware. Helping ourselves to permanently fix the problem is the best answer in the long run. Gets to be a political football with developers and homeowners who have lived there for years though.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com