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I have a retaining wall that is on the property line. Along the top of the wall is my driveway. Part of the wall has given way and needs to be rebuilt. I think I have everything figured out except how to compact the backfill as I rebuild the wall.

What type of tool or method can I use to make sure the fill is compacted?

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Why did the retaining wall fail? There's no use in repairing it just to have it fail again. –  longneck Jun 12 '13 at 17:54
    
Usually, bad footing, poor drainage and water pressure behind the wall. –  Fiasco Labs Jun 13 '13 at 3:41
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2 Answers

up vote 2 down vote accepted

You do not give details on how large an area you got to back fill. You mentioned part of the wall under the driveway. Relatively speaking that is a small area. Too small to use a "vibrating plate compactor" !

Using that will unnaturally force your back fill downwards and then sideways - damaging your wall all over again! And it wont compact it properly because it does not magically remove air pockets and other crevices.

We had to do this allot when building on uneven places and do this under driveways too.

The best way to do it is layer by layer.

  1. Backfill layer of rubble (mixed with some ground is ok) (something like 30~60 cm)?
  2. Dump normal ground on top of it
  3. Hose it down with water. You should see the ground disappearing into the backfill, dump more ground until it is filled and overflowing. DO not flood it just get a reasonable stream of water. At this point the ground is naturally compacting(and getting rid of air space)
  4. When you reckong its pretty much not going to fill any more dump a thin layer of ground and damped it.
  5. Let it stand for while (15 minutes i n hot sun) and repeat from 1 till done.

This takes some time but will last for very very long time. When it rains, the ground is already water compacted so it wont subside. It also does not create shock damage to your retaining walls.

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A vibrating plate compactor ( Wikipedia link ) would typically be used to compact the backfill, which is usually laid in layers of approximately 150mm to ensure it is well compacted, especially when using stone backfill containing a lot of fine material (which will compact very well). Re-using excavated material doesn't always compact as well. Depending on the design of the wall though, you might need to use a single-size stone backfill to ensure that water can drain through to prevent water building up behind the wall.

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That is the worst thing you can do!!!!!!!!!!!!!!!! –  ppumkin Jun 13 '13 at 9:18
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