Hydrostatic pressure between shoring and basement wall

[Shahe2015]

This question comes often, what is the hydrostatic pressure if there is a buildup between a caisson (diaphragm) wall and basement wall. According to physics, width of water column does not impact hydrostatic pressure. Hard to imagine 1” of water column would produce same pressure as a lake. Looking at analyzing an existing condition where drainage failed at bottom of a 4 levels underground basement.

Looking for papers discussing this.

 

[HTURKAK]

If drainage failed , the hydrostatic pressure will built up with raising of GWL and at the bottom of a 4 levels underground basement will be ,

P= γ*H*4 +γh ( γ= unit wt of water , H story ht , h = height of water btw the top level and GWL ) and in short,

P = γ*Wh ( Wh is the water height btw bottom of basement and GWL )..


Lateral pressure of soil , granular material will be different depending on the dia. / or thickness as in the case SILO walls ..

But , in case of liquid , the hydrostatic pressure free from dia.. ( only the unit wt and ht are effective ) The negligible exception is the capillary effect .







Not to know is bad;
not to wish to know is worse.

NIGERIAN PROVERB

 

[phamENG]

If you have a space with 1" of water filled to the same depth as a lake, it would exert the same pressure as that lake. Here's where volume comes into play: as the wall moves under the pressure, the proportional volume change will be huge for your 1" space, but negligible for your lake. So deflection in the wall will cause the water in the 1" space to drop quickly and arrest the deflection in the wall. For a lake, the level really won't change, so the pressure won't change, so it'll just keep pushing until the wall collapses and lets your lake into your basement.

So I guess the question becomes - how much will it deflect and will that water keep filling that space? Because if it doesn't deflect or the water keeps replenishing itself, it'll have to keep holding that height. And really, the effort you'll have to go through to calculate all this will be way too precise while not being very accurate. Probably best to just consider the water pressure in the gap.

 

[la belle vie]

Even 1/100 inch of water would generate the same pressure as a lake. Is there anyway you can drain the area? The Schoellkopf power plant disaster is a good example. They grouted up a bunch of pesky leaks on a rock face not appreciating there was a vertical joint in the rock parallel to and a few feet in from the face. Pressure built up and the rock face collapsed, taking down the power plant and killing one worker.