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

• 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

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

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