Buttress Dams Stability Anaylsis

[kmerl]

I have a project involving a buttress dam. The dam is founded on shales, I need some references for the determination of stability values. Slide, foundation, overturning, etc. One of the main issues is interaction of the "thin" section with buttress section and the loading that each implore on the foundation materials.

Intially I am thinking of doing global on both the thin and buttress seperatly, but I think that is flawed. I need to be able to resolve the reaction loads applied to the buttress from the thin section.

Keithe J. Merl

 

[Focht3]

Where is the structure? (State only.)

Have you done any research on similar dams? Reviewed the USCOLD publications? Those might help you somewhat - but a good mentor is better than any textbook or reference when it comes to good dam design.

You called the structure a "buttress dam" - could you be more specific? Is this a new structure, or an existing one? (I will assume, for now, that you are talking about an existing structure.) How old is it? Is it a concrete structure, or earthen? Who built it? Dimensions?

Shales are tough; there is never enough detail (in my opinion) when dealing with these rocks. Be sure to review the Waco Dam failure and its remediation before you get too far along in your project -

[If it's an Amberson-type dam, let me know. I have a great consultant for you on these structures.]



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

 

[BigH]

There has been a lot of work of dams on shales but, unfortunately, I have no references directly ready with me at present - check out dams in Saskatchewan and Manitoba - Bearpaw Shales, I believe. I also have a couple of names of retired engineers who have great experience on this topic. I'll try to find out some info for you.

 

[kmerl]

Focht3

If you me open faced slab buttress type dam, you are on the right track. I have been pondering this issue over the weekend and have come up with an idea.

By the way...
This site is located in Princeton, New Jersey. It is exisitng, it is located at Carnegie Lake. I have very limited information on rock characteristics, and need to determine how much detail I need.

These dams can't be considered as gravity neccessarily, they don't rely on gravity. I have to determine a method to apply the web loads to the buttress and determine the stability of the structure as such. I feel that basically applying FBD to the web and buttress is probably the best method.

Therefore treat the web as a anchored cantilerver wall free to rotate and then apply those loads to each buttress. Thereby appling a lateral load as a moment about the base of the buttress.

Thoughts would be helpful, as a note I am ignoring the inter stability of the structure, I have S. Engineer taking responsibility for that. My conern is the ability of the roack to support the structure and the golbal stability.

Also I am considering coring throught the dam into the bedrock to determine the rock coniditons, once again suggestions greatly welcomed....

As always much thanks....



Keithe J. Merl

 

[cap4000]

I have never done a buttress dam however it is very similiar to a Counterfort Concrete Retaining Wall Design.
Basically, the wall spans horizontally to the buttresses.
The Buttress acts as a large Moment Couple stabilized with rebars tied to the thick base slab and wall.The base slab spans to the buttresses. Hope this analogy helps. Good Luck
as this is a unique design procedure.

 

[kmerl]

Thank you cap4000

That sounds like how I have to consider this, i.e. it is a series of counterfort concrete structures in series. That sounds like a great analogy....



Keithe J. Merl

 

[BigH]

There has been a lot of work in Canada on rehabing dams - especially for the paper mills. My mentor (M.A.J. Matich) has written quite extensively on the subject. I will try to find the references. It is imperative in the rehab that you know the nature of the contact of the existing dam and the rock surface. Your work, in the end, may likely involve rock anchors to tie the dam down "better" into the rock. Will advise as soon as I can on the references.

 

[Focht3]

If you look at a cross-section of the dam, do you have a "hollow core" with a concrete face upstream (and possibly downstream) - with an internal diaphragm buttress every 10 to 40 feet or so? An on-line photo of an Ambersen dam can be found at the following link:

http://www.ecih2o.com/PROJECTS/DAMSFTYproj/Logan.html

In my opinion, you need to do a thorough background study of the dam before you start making stability analyses. And you need to identify the dam type and research the known problem areas for the type of structure that you are evaluating. This becomes more important as the age of the structure increases -

Does the dam generate electricity? If so, you need to contact FERC as soon as possible - they have jurisdiction.



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

 

[kmerl]

Focht3

Thanks for the link I will research soe of those articles.
The dam you are describing is similar, however much bigger scale (ours is smaller). From the research to this point there is no hollow portion, it is a solid structure the maximum height from ground surface is approx. 14ft. There is only low level outlet structures, no energy generation.

I will be researching the data at NJDEP, and MUDD library on the dam. It was constructed in the 1930's and several maintenance iterations were completed including installation of upstream sheetpiling and mass removal by installation of a "v" notch. The dam is 700 feet long and is filled by a considerable watershed. The Dam is a Class 2 due to downstream inundation flooding.

We are hoping to surmise the rock contact by way of the research, however if our reasearch comes up short some coring will be neccessary. I was been determined that FERC is not the governing body here, NJDEP Dam Safety is calling the shots.

Fortunately I have a dam owner that knows some work needs to get done, and has a little money to do it.

BigH
I am seriously considering the cable stay, becasue it is a historic dam. Visual modifications could conflict with the Historic Stucture ordinaces and state rules. I agree that the foundation will become greatly important with this solution and indepth investigaiton will be warranted. All references are greatly welcomed..

cap4000
I would be interested in any references you could offer for the counterfort design procedures, these would help in determining where I'm going with the modeling.

I will keep all updated.....
Always thank you for you help and suggestions...



Keithe J. Merl

 

[Focht3]

Is it solid concrete, or rockfill with a concrete face?

FYI, Ambersen-type dams were still being built in the 1930's.

When you core, be damn sure the driller has appropriate packers, valves, etc. - in case you hit a fracture that is hydraulically connected to the reservoir and the top of ground is below the pool level. The driller needs to have experience dealing with artesian conditions, just in case...



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

 

[kmerl]

Good suggestion, from my knowledge it is solid concrete, however more research is to come. We may be getting some pictures from the original construction....

Keithe J. Merl

 

[Focht3]

Post them on-line and put the link in a future message!



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

 

[BigH]

Reference on Rehab of Ambursen Type Dam:

Matich, MAJ, et al., “Rehabiliation of an 80 Year Old Ambursen Type Dam”, Proceedings, 2nd Annual Canadian Dam Conference, Sudbury, 1999.

 

[cap4000]

I have 2 good references that should help you: Designed of Reinforced Concrete Structures by Allan Williams,Ph.D 2000 edition and the Foundation Engineering Handbook by Winterkorn and Fang 1975 edition. Good Luck.