Retainer wall problem


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Old 08-21-07, 03:04 PM
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Retainer wall problem

We have just installed a 100' long retainer wall it is 42 inches tall at the highest point and 24 inches tall at the lowest point. We buried the first coarse and built the wall. We used clear limestone for backfill. We put in a properly sloped drain tile before the backfill was all in place. We used Anchor Block Diamond series blocks. The problem is when it rains water comes up from below the block in a couple areas. It mostly spits out mud, but also spits out some of the class 5 base. I have never seen a wall do this. Thanks for any help JT
 
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Old 08-21-07, 05:40 PM
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I am not sure of the terminlogy of your fill, but obviously your drainage arrangements are not sufficent.
 
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Old 08-21-07, 06:00 PM
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fill

Thank you for the reply. The fill I used is 3/4 to 1 inch limestone. Clear meaning no fines. Is it possible to use to much fill? We used about 12 tons of backfill. Thanks again. JT
 
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Old 08-21-07, 06:02 PM
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What is the slope above the wall? Is it flat or receding from the face? It should have enough slope and impermeability that the majority of water flowing across the surface will either exit beyond the ends of the wall or in heavy rainfall situations flow over the face. If you have that fill and mud boils, you either need to re grade above the wall or provide drainage pipe at the base exiting to sunlight. Your wall will fail as is, probably sooner than later.
 
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Old 08-21-07, 06:04 PM
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Retainer wall problem

The fines from existing soil and from the Class 5 are probably being washed through the one size backfill.

Did you use any fibric filters around the drainage pipe of between the fine and coarse soils?

Dick
 
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Old 08-21-07, 06:45 PM
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drain tile and grade

Thank you for your reply . The drain pipe is covered. 100 feet of corrugated flex pipe with cover /filter . The pipe does exit to sunlight.
There is a gradual slope above the wall. The soil is clay and gets very silty when wet.
I have installed erosion control blankets above the wall because we recently seeded. The blankets cover 24'x100' area.
Is it possible this problem will go away once the grass is growing? Thanks JT
 
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Old 08-21-07, 07:08 PM
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Yes, it sounds like you did it right, but received a lot of rain as soon as you finished the project. At any rate, there is not much you can do short of tearing it down other than letting it ride to see how it settles in.
 
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Old 08-21-07, 07:55 PM
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rain

Tscarborough, You are correct we have had two major rain storms in a 6 day period. I put the erosion control blankets down 4 days after the first storm, to hold things in place.
I have really tried to do this right because this wall protects an in ground swimming pool.
I thought I would post this to see if I have missed anything. Or if anyone has seen this before and what they did to fix it.
Thanks JT
 
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Old 08-23-07, 12:23 PM
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jtburke, you can never use too much granular fill to replace the original clay so long as it's the right kind.

Just as Concretemasonry stated, the fines that you say are in the original soil are no doubt migrating through the very pourous crushed stone that you used, especially if you didn't use a geotextile below the crushed stone to prevent the fines from migrating upwards through the coarse material. Silty clays are the worst soil for instability under wet conditions.

A good thick layer or two of 7/8 inch well graded crushed gravel would have worked much better for you, but that's too late now, so all you can do now is hope that it holds up OK.
 
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Old 08-23-07, 02:21 PM
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one other thought

Thank you Quickcurrent for your reply. The leak in the wall is in two areas. It comes from two blocks in each area. Could the drain tile have gotten crushed during backfill? I was in the bobcat my son was in the trench. I think this weekend I will dig out the backfill in the worst area and have a look. If that does not workout I think I will hire someone with a sewer camera to have a look. Any thoughts? Thanks JT
 
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Old 08-23-07, 07:14 PM
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Originally Posted by jtburke
Thank you Quickcurrent for your reply. The leak in the wall is in two areas. It comes from two blocks in each area. Could the drain tile have gotten crushed during backfill? I was in the bobcat my son was in the trench. I think this weekend I will dig out the backfill in the worst area and have a look. If that does not workout I think I will hire someone with a sewer camera to have a look. Any thoughts? Thanks JT
You could hire someone with a sewer camera, so long as the camera fits in the piece of pipe you put in, but it may be expensive for such a small length!

It's possible that the pipe got crushed depending on what type of pipe it was and how it was handled. You're probably in the best position to know if that might have happened. Crushing it in two places enough to prevent water flow seems like a stretch to me though. I think it's more likely that the fines migrated and could be blocking the pipe. But anything is possible.
 
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Old 08-23-07, 07:18 PM
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Water will find a path and enlarge it. If it is a major concern, dig out behind the wall at those two points and repair the backfill.
 
 

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