An arch shaped dam wall. Image credit MediaWiki

An arch shaped dam wall. Image credit MediaWiki

ZIMSEC O Level Combined Science Notes: Dams

  • Dams usually fail due to lack of stability rather than lack of strength
  • The sideways thrust of dammed water can topple the wall
  • This thrust varies from when the dam is full and when it is empty
  • This will likely cause cracks to appear on the wall
  • Also if water seeps into the dam wall it might damage the masonry
  • and exerts a lifting force on the wall
Jacking a dam wall

Jacking a dam wall

  • Dam walls are expensive to construct
  • The amount and thus cost the cement used can be reduced
  • by reinforcing the concrete using steel rods
  • The steel rods are embedded in the solid rock beneath the foundations of the dam wall
  • The vertical steels are anchored in bed rock and taken up through the concrete as it is laid
  • At the top the rods are stretched using a jacking device at the top of the wall
  • stretching (tensioning) the rods makes them more effective and makes the dam more stable
  • The dam wall is also wider/thicker at the bottom where pressure is greatest
Arch-shaped dam wall

Arch-shaped dam wall

  • The walls can also be arch shaped so as to reflect and spread the pressure of the water.
Earth dam wall

Earth dam wall

  • Dam walls can also be made using earth instead of concrete
  • Earth dams have thicker walls
  • Use more materials to build
  • They are cheaper to build but are not usually as strong and
  • are usually limited to smaller dams

To access more topics go to the Combined Science Notes page


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