Stilling basin

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Stilling basin below the dam of the Okertalsperre empty and ...
... with the bottom outlet open

As a stilling basin (of tosen ) is referred to in hydraulic and civil engineering , a braking catch basin for the draining water of a dam , a dam , a weir , a flood retention basin or a different type of storage system.

It is used to mechanically delay the flow when the water overflows at high speed - especially at high tide - and falls into the stilling basin. The stilling basin is the lower part of the flood relief system and is also called an energy conversion system because the kinetic energy of the flowing water has to be converted into heat and sound energy . The aim of the energy conversion is usually a jump , that is, the transition from the flowing to the flowing discharge.

In order to prevent the rinsing out of the river ( scour formation ) in the underwater , the stilling basin usually has a bottom and walls made of concrete . Concrete blocks or boulders (so-called disruptive bodies ) in the stilling basin, against which the water collides, increase the energy conversion. In the stilling basin, the water can calm down before it flows further downstream. Depending on the geometry of the pool, it may be necessary to install an additional concrete end sill at the end of the stilling pool. This ensures that the alternating jump always occurs within the stilling basin, even with different flow rates, and does not migrate into the underwater.

The so-called bottom outlet usually also ends in a stilling basin.

In order to support the calming of the water, the jumps for the overflow protection of dams often have concrete or other obstacles in the form of smaller teeth at their end. As a result, the water mass is already distributed in the air, fanned out and already slowed down by the air. In this way, the massive jet is already reduced before it hits the stilling basin.

Since the physical processes in a stilling basin are difficult to determine by means of calculations, the function of larger stilling basins is usually checked by means of hydraulic engineering model tests before they are constructed.

Small stilling basin of the southern tunnel at the Forggensee power plant . On the right in the picture the large stilling basin with overflow and flood relief

Individual evidence

  1. a b c Bretschneider, Lecher, Schmidt: Pocket book of water management . 6th edition. Paul Parey, Hamburg and Berlin 1982, ISBN 3-490-19016-5 .
  2. ^ Rißler, Peter: Talsperrenpraxis . R. Oldenbourg Verlag Munich Vienna, 1998.