Dear All, I am dealing with quit

[hari]

Dear All,

I am dealing with quite number of Dewatering problems in tendering stage as well as for working jobs in varied type of soils(sand/Clay, Rock).

I have a problem in deciding the thickness of aquifer that should be taken in the standard formulae(For unfined and unconfined),because the Bore hole details may not be available to the full depth of aquifer(example, a sand layer of infinite depth and we do not know where the impermeable layer like rock is there).

In those situations what should be the thickness of the aquifer should be taken ,for dewatring of say 6m in aquifer?

Please enlighten me in this regard.

Thanks and Regards

Hariharanath.K
L&T,ECC

 

[reddog99o]

You should take the thickness of the aquifer as the difference between normal Ground Water Elevation and the level to which you wish to dewater. I'd add a couple of meters here so that the bottom of your excavation is not always sitting on the hydraulic gradient. Whatever you do, make sure you leave the entirety of the exposed aquifer exposed to screen. If you don't need all of the screen then you can throttle back your pumping capacity to maintain the hydraulic gradient where you want it. Observation wells read with significant frequency are key to successful dewatering operations. "More is Better" when it comes to dewatering because you can always scale back, but depending on the situation, you may not be able to add more capacity.
Good Luck, and gimme' a holler if you need anything else.

Best regards, R.A. Hassett, P.E.
rah1616@hotmail.com