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

Quick NetOne, Telecel, Africom, And Econet Airtime Recharge

If anything goes wrong, chat with us using the chat feature at the bottom right of this screen