Cement Bag Retaining Wall

[WoodChuckDad]

I have searched the old forums and only been able to find one thread on a retaining wall made from stacked cement bags. It isn't anything revolutionary, but it is something that I have not done before. I am creating a bridge crossing over the dam overflow of my pond. I hired an engineer to speck out the pipe needed and he gave plans for the bridge as far as the pipe needed and the grade but the retaining wall is up to me. The plans call for two 48 inch pipes, 60 feet long put in at a slope that takes the exit end10 feet below the entry end. At first I was going to use a precast headwall but the cost delivered will top $10,000. Also it would weigh around 6,000 lbs so maneuvering it into place would also be a challenge. Instead, I am going to use stacked 80 lb backs of quicker, pinned together with Rebar. I will come up 2feet above the pipe so total height will be 6 1/2 feet. I have ordered 400 bags of concrete to be delivered on the same day the pipes are to be delivered. I have seen a few threads about building retaining walls so I assume following the same principles would make sense. Should I put 1 inch gravel between the wall and and back fill? and if so, how much and how high?

 

[countrybumpkin]

Google " bag Crete retaining wall" you'll have plenty of reading and ideas. They also make special bags for building walls.

 

[WoodChuckDad]

I contacted sakrete about the project. The guy I spoke to said they have to hat production and do a special run for those bags and I wouldn't be able to order less than a trailer. He also said it would be 9-11 dollars per bag. He advised me to just get it at lowes and use the regular 4,000 psi bags. So, I'm pushing forward.

 

[EddieWalker]

How are you going to stop water from flowing along the outside of your pipes?

Once your trench is dug for the pipes, it will be 100% impossible to get good compaction all the way around it, which means the soil used to back fill will be softer then the compacted soil already there. This will give water a path to travel.

The sacks should work OK as rip rap to cut down erosion from the waves of the lake, but it will not stop water from flowing through it and down the sides of your pipe. You will have to build forms and pour concrete, and after you remove the forms, seal the concrete and where it contacts the pipe with some sort of water proofing. This will be a thousand times easier to do now compared to later when you discover the leaks you will have.

 

[WoodChuckDad]

Eddie Waker, Where's the love, man? Don't tell me that. There is a spillway tube in the pond. I've never seen a wave on that pond at all. Currently the overflow creek is dry. When we have been having lots of rain it gets about 2-3 inches in it and about two feet wide. These pipes are sized for the 100 year storm. My plan is to start by diggings own a foot and building a faoundation that rises up 6 inches above the creek Then do the stacking on top of that at a slight angle toward the bridge. I figured this would give the water some direction toward the pipes openings and give time for soil compaction. There will be a 50 foot wide trapezoid of earth on top going from end to end over the pipes. I can't imagine I need to go higher. The engineers original plans just had me doing earth with rip rap on it at a 1 to 3 angle. (1 up and 3 over).

 

[WoodChuckDad]

So now you have me thinking and worrying. I may build up the base line to a foot above the inlet line. Like you said, better now than later. I'll take lots of pictures.
This is what I am going to be crossing....gently building up from where I am standing to the crest on the left. The area of the downed trees over to the right is about where I will have the retainer wall.

 

[davrow]

Check out this youtube video of a guy using lunch bags (instead of full concrete bags) to build the wall around a culvert. It is an existing culvert instead of a new one.
It is two parts, building it, then how it works in a good rain. (this is just part one, need to search youtube for part two if interested)

 

[Ed of all trades]

Davrow thanks for the video, might use that idea. Ed

 

[WoodChuckDad]

I've come across that one. Like the way it turned out. Our soil compacts really well here I think that I should have pretty good luck with this. Materials will be delivered this week. And I will start work on it next weekend. I'll post pictures when I get them.

 

[Rustyiron]

I've dry stacked several "headwalls" for pipes over the years. No problems at all and the paper just go's away in a year or so. No special backfill, I just try to make a tight fit at the pipe and between the bags and don't be stingy with the rebar.