Dam Building

[Gerbil007]

A dig I'm working on has turned into a bit of a siege. There's nothing for it but to start a bit of civil engineering and build some dams.
I'm thinking our best bet is probably cement. I was thinking of building a sort of dry stone wall, then using the cement to plug the gaps and make the thing water tight. Anyone with experience care to offer a critique of the plan and any other tips?

 

[Brains]

Surface or underground?
what would be the consequences of a collapse? the worse the scenario, the better the dam has to be!
Add in a pipe as a drain, with a suitable plug that can be removed from the dry
building in a plastic sheet as a membrane will also help, and temporary dams can be made very well with sheeting and support - lay planty of spare upstream which will act as a seal as the water depth increases
As a rough guide, a batter or slope of 45 deg on both faces would be a good idea, a shalloer angle if possible

 

[bograt]

Horses for courses, depending on location/ amount of water to be retained or controlled/ permanance, etc., I often found that taking a few woven polyprop sacks down and filling them with what is available (sand, silt, mud, clay, etc. NOT stones) works well in the short term, you can "puddle" any gaps with clay or mud to good effect, or cover the front with plastic sheet, I agree with Brains about keeping a good "batter" on it and including an easily bungable outlet pipe.
If a more long lasting arrangement is required later, the dam can be drained using the outlet pipe and the whole thing faced with weldmesh and concrete.

 

[hrock]

all good advice so far but really you will have to tell us more about it to get more on topic advise.

i have done a fue small ones with post-crete and the odd bit of plasterers corner metal cut up.

just put a bit of pipe you can plug or connect up as low as you can and mix it up about 2 hand fulls at a time in a darren drum and then (whareing gloves as its nasty stuf) put it on and hold it in place. whalst your friend washes the darren drum and mixes some more. once above the water you can mix bigger loads till the hight required is achieved.

but some people have had good sucksess with 2 bits of wood cut to fit and samwitching a bike innertube of the right size between them as you squash them together with some bolts and wing nuts the tube forms a seal on the passage wall.

oh and on a side note if you want concrete to stick to caves and cave rock take a scrubbing brush and clean them well.     

 

[Ground Trog]

or rockbolt.