2007-08-21 03:59:08 · 7 answers · asked by chato r 1 in Science & Mathematics ➔ Engineering
Because there is more hydrostatic pressure from the water at the bottom, than at the top. The concrete has to hold more pressure, so they make it thicker to hold more pressure.
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2007-08-21 04:03:09 · answer #1 · answered by tlbs101 7 · 1⤊ 0⤋
The answers above are correct regarding the hydrostatic pressure of the water acting against the dam; however they have neglected a few variables related to the geo-technical design.
If your question is in regard to earth embankment dam you must also consider the phreatic relationship of the water surface elevation. In other words the saturation of the compacted dirt may cause it to fail. National Resource Conservation Service (NRCS) has a pond code #378 which is the bible for building earthen embankments in northern America.
If you question is purely about concrete dams you must also consider the saturation of the native soils undermining the supporting subgrade of the dam (assuming that there is not an impermeable liner). The soils may "liquefy" and not be able to support the weight of the dam. Another factor to consider is the footer/foundation design of the dam.
All of these factors and more contribute to the overall structural, hydraulic and geo-technical design of the dam.
2007-08-21 12:54:06 · answer #2 · answered by bradlelf 2 · 0⤊ 0⤋
The Static pressure exerted by the head of water increases with depth and, this pressure acting on EACH cm², or in² or m² of the total area of the structure can compute into Hundreds of Millions of Tons of force acting on that area.
The deeper the water, the thicker the dam base will be.
2007-08-21 20:24:54 · answer #3 · answered by Norrie 7 · 0⤊ 0⤋
For stability, and because the water on the bottom of the dam has more water above it causing it to me more pressurized. The bottom of the dam would need to be stonger because of the pressure on the water.
2007-08-21 11:04:15 · answer #4 · answered by Gwenilynd 4 · 0⤊ 0⤋
They have to have a thick base otherwise they wouldn't be able to stand up to the horizontal pressure of the water they are damming up.
They also have to be able to support their own weight.
2007-08-21 11:03:29 · answer #5 · answered by Anonymous · 1⤊ 0⤋
You also need to consider the overturning moment of the dam.
2007-08-22 00:09:23 · answer #6 · answered by ? 6 · 0⤊ 0⤋
It has to do with lavage. Light poles are thicker at the bottom as well
2007-08-21 12:03:25 · answer #7 · answered by David Dodeca 5 · 0⤊ 0⤋