Retaining wall base preparation and drainage

Discussion in 'Landscape Architecture and Design' started by conepile, May 15, 2003.

  1. conepile

    conepile LawnSite Member
    Messages: 78

    As I mentioned in earlier posts, I don't normally do walls, but my client asked, and I'm willing. Besides, it is pretty small.

    I am installing a retaining wall next week and have a question about base preparation. The wall is on a slope, so the base will be stepped. The base will be 8" deep (the area was disturbed when a basement was dug two years ago). My question: What is the best way to install the base, to make packing it easiest/most time-efficient? I'll use a plate compactor, but the runs before each step may be pretty short. The wall slopes from 0 to 3 feet in height over a span of 30 feet, then slopes back uphill to 0 feet again in just a 15 linear foot curve.

    One other question: I'll backfill with stone, and have perforated drain tile at the base. Since the wall slopes uphill in both directions, I don't have a convenient way to discharge the drain tile. Is it necessary that I even bother to do this? I was thinking the open tile would be enough to reduce the hydrostatic pressure on the back of the wall, and the water could weep through the blocks. Any recommendations?

    Thanks for any comments or feedback.
  2. ksss

    ksss LawnSite Fanatic
    Messages: 7,168

    Your probably well into the project by now, but I would be very concerned if your building a wall over disturbed soil as deep as a basement. If the hole was not compacted in lifts as it was backfilled. I would anticipate settling. A plate compactor would provide no help in preventing that from occuring. I use compacted 3/4 crushed roadbase as foundation with washed rock behind and depending on soil conditions I place weed barrier between the rock and soil. I typically try to route drainage from downspouts out from the wall with underground piping. However rainfall is a bit of a rarity out here. Probably more of an issue in other parts of the country.
  3. conepile

    conepile LawnSite Member
    Messages: 78

    The area where the wall is going is outside the excavated area from when the basement was dug, but had still been disturbed when the lot was rough-graded, as well as when the basement was backfilled and the lot graded again..

    I had the wall area excavated yesterday and am starting the base today.

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