Ground Drainage input advise, on New retaining wall.

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Old 10-04-14, 09:44 PM
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Ground Drainage input advise, on New retaining wall.

I am in the process of reconstructing a retaining wall ( existing of cinder blocks) that was ready to come down. Due to the overgrowth of a very strong root and a lousy drain that filtered into the wall which was helping in destruction during frost contractions during the winter season. It held up and did its job for a 55 year old.

The new wall will be a stone and cement mixture. I am planning on putting a good varying gravel base of 6+ inches under the new stone wall, for drainage. New Wall is approx. 16” wide x slopping height of 8 feet down to about 2 feet. with an overall length of ten/ twelve feet.

Question at hand... I would like some input on the new passive pipe drain I plan to put about a foot away from the wall and underground approx. two feet. What I had in mind was a six” (or larger) pipe with one inch holes on top covered with a fine screen mesh (to keep dirt out) and carry it two feet past the end of the wall.
Any input would be greatly appreciated. I hope I explained myself clearly enough.
If you need picture I can try and post some.
thank you
 
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Old 10-05-14, 06:12 AM
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You said what you are going to build the wall from; stone and cement. You did not describe the wall's construction. How are you planning to build it?

I would not bother with 6" pipe. 4" perforated pipe will be more than sufficient to carry the water. I would run the drain pipe at the bottom of the wall with a sock to keep out dirt and have clean gravel behind the wall up to the surface for drainage.

Position the holes in the drain pipe toward the bottom. Water may drain down from above but it will build/percolate up from the bottom and you want it to get into the pipe as soon as possible which is the bottom. Black corrugated pipe will work but I prefer rigid PVC as it's smooth interior makes it more resistant to clogging. Being rigid it also resists having dips that can collect and hold water.
 
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Old 10-05-14, 07:13 AM
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would NEVER use socks - i think most do because the apron/vest stores sell the stuff but understand this - they're in biz to sell stuff, not provide mtls for well-designed/engineer'd projects,, matter of fact, my stars just did a job completed whilst by bride & i were in china - when i got back, we tore it out then completed it as proposed,,, the sock allows silt to be stopped too close to the pipe impo,,, we do install filter fabric in the trench however the trench is 1'd x 1'4"w x length,,, that's a total of 40" of fabric compared to the sock's 12.57"

compacting granular base creates a flexible foundation,,, typically the base should be 2x wall width w/wall center'd,,, we prefer 4" s&d perforated pipe,,, we wouldn't place the pipe lower than the top of compacted base mtl tho

hope this is clear & understandable,,, we also use 6" of #57 stone for backfill next to the wall from btm to top
 
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Old 10-05-14, 02:06 PM
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Good point about the sock's surface area. It's probably much, much worse when you figure that the sock is tight around the pipe so water can only penetrate where there are holes in the pipe.



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Where were you in China? I just got back from Shanghai.
 
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Old 10-07-14, 09:23 AM
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ck your pm's,,, i don't want to jam this thread,,, thanks, dane
 
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