Dam Wall
Dam Wall
(OP)
Hi.
An acquaintance of mine owns a farm with a through-flowing river. He would like to increase the wall height of an artificial retention dam wall by approximately 800mm(See attachment). The 800mm increase will cause the top of the wall to be flush with the higher, inclined water retaining wall to the right of the weir.
1. Is the 0.8m increase in height(Add. 7.85kn/m2 at the base) significant enough to reconsider the design of the existing dam wall, or can concrete just be poured on top?
2. Can anyone provide a source that would enlighten me as to how to go about the design? and the concrete works?
Thanks in advance.
Jaco
An acquaintance of mine owns a farm with a through-flowing river. He would like to increase the wall height of an artificial retention dam wall by approximately 800mm(See attachment). The 800mm increase will cause the top of the wall to be flush with the higher, inclined water retaining wall to the right of the weir.
1. Is the 0.8m increase in height(Add. 7.85kn/m2 at the base) significant enough to reconsider the design of the existing dam wall, or can concrete just be poured on top?
2. Can anyone provide a source that would enlighten me as to how to go about the design? and the concrete works?
Thanks in advance.
Jaco






RE: Dam Wall
RE: Dam Wall
I have posted this thread in the civils forum, but figured that if point 1.(civils) in my post does not apply, point 2 which is a structural issue, would be appropriate for this forum.
RE: Dam Wall
Assuming I am correct, the overturning moment on the footing below the dam won't increase. However, the vertical load will increase, so I think the footing should be checked for the new loads.
DaveAtkins
RE: Dam Wall
RE: Dam Wall
Thanks. The weir will also be lifted, hence lifting the water level. The aim is to widen the retention pond/dam(Increase water volume). The additional concrete, like noted by yourself, will require me to reanalyze forces on the footing below the dam wall. I can only assume that the additional weight of the water on the footing will also come into play.
Seeing that a design is not available, or the fact that I cannot visibly asses the geometry/properties of the footing; is there some way I can arrive at a conclusion about the current properties of the footing by considering the geometry & design of the dam wall? The water retaining properties of the wall must have some relationship with that of the footing as they work together in ensuring stability.
csd72 - Thanks. But erosion is not an issue.
RE: Dam Wall
Any permanent height change to the spillway will affect the stability of the dam structure by increasing the ultimate pool height during spill.
As this is a gravity retaining structure, the analysis should not be too complicated if the dimensions are known.
I just wonder why stoplogs could not be used in lieu of more concrete. Could be simpler with only a .8 meter, or less than a foot increase in the pool height. These can be easily pulled if a problem is encountered.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Dam Wall
Raising the dam wall will affect the stability of the wall. It is a basic gravity structure and the analysis is straightforward. The only tricky bit is the asumption on cohesion between the rock foundation and the concrete. From the piccie it seems as if the back slope is quite steep and you may have to rely on cohesion.
The USACE has great publications that you can download, look at the one for gravity dams and you will find all the info you need to calculate the stability.
I would be concerned about erosion, the overall flow depth will decrease but the water on the sides will spill on the banks and it may not be competent rock
There is also not visible energy dissipating structures and downstream erosion is likely
RE: Dam Wall
RE: Dam Wall
The structural issues are minor here. The big issue is dealing with your state's Department of Natural Resources. They may not even allow this, even if this is on private property, because it affects everything downstream.
DaveAtkins
RE: Dam Wall
Who owns the Right of Way on the river?
Are code authorities involved?
Is a permit required?
Michael.
Timing has a lot to do with the outcome of a rain dance.