Basement subjected to uplift

[dccd]

During the design of basement, why do we need to consider the uplift of the basement subjected to hydraulic uplift ?

When the excavation happen, watertable drawdown occur at the exacavted part.

When the excavation finished, the watertable already at the base, why the basement will be subjected to uplift ?


Can someone help to explain on this ?

 

[HTURKAK]

The following is excerpt from ( Groundwater Lowering in Construction , by P. M. Cashman and M. Preene )

The groundwater lowered during foundation construction.Then the pumping is stopped and the GWL raises to original level and uplift pressure builts up .

If you put garbage in a computer nothing comes out but garbage. But this garbage, having passed through a very expensive machine, is somehow ennobled and none dare criticize it. ( ANONYMOUS )

 

[TerryScan]

If the water table was high enough to require drawdown during excavation, why wouldn't the water table return to original elevation when the work is complete? Is there a post construction dewatering system?

 

[HTURKAK]

Even if dewatering continues after construction, still the finished structure shall be safe against uplift / floating.. ( GWL may raise to original level due to some risks, power or pump failure ..)









If you put garbage in a computer nothing comes out but garbage. But this garbage, having passed through a very expensive machine, is somehow ennobled and none dare criticize it. ( ANONYMOUS )