Retaining Wall Failure
Retaining Wall Blowout
Well, this is not a sight that you want to see on your property. As you can see, we have a retaining wall failure. I was given a call by this client of ours to come out and take a look at this wall and see what we could do to help them with it. This is not a wall that we built. This wall is seven years old and the remainder of the wall runs down the side of the driveway looks to be in pretty good shape. So, they came home one day after a hard rain storm and noticed that this wall had fallen down.
Let’s take a look at why this wall failed. If we look into the next door neighbor’s yard, we will see a beautiful new landscape. Look at all that nice rock work and those nice rocks stairs. However several weeks ago this was all wooded and this hillside was not clean and pine straw. Rather this hillside had a lot of vegetation on it. That vegetation prevented a lot of silt sediment from washing downstream. So, you can see this water comes downstream into this low point. What happens is it created a channel.
Behind Retaining Walls
I want to show you what happens behind this retaining wall. As I mentioned, this retaining wall was seven years old. Water is designed to travel down behind it into this gravel creek bed and carry the water out. For the last seven years it, as worked perfectly. However, as part of the finishing stages of their landscape, the neighbor put pine straw mulch all through here. So the evidence is very clear to me as to why this wall failed. There is a clear delineation where this rock bed begins and travels all the way down again behind the wall.
This water has traveled down and has pushed this place through. It gave the water no choice but to go behind this wall creating a lot of hydrostatic pressure (which is water pressure built up) at the base of the wall. Thus blowing it out, and this is what we call a sudden retaining wall failure. So, we’re going to come back and we’re going to put this wall back together. I’m looking to find a lot of clean 57-stone gravel which is a washed gravel and a black pipe to indicate that there’s a French drain back, and we have neither. So, what we have is marble looking gravel which does not compact well. It has a tendency to roll over itself and just basically creates gravel and dirt soup.
Rebuild the Wall
We’re going to come back and rebuild this wall, and we’re going to install a French drain. Then we’re going to reinforce it with Geo grid which is an engineering mesh material. That way we can give our stamp of approval on this wall and let this homeowner know that they have nothing to worry about. We’re going to guarantee to them this is not going to happen again. To prevent these blowouts, make sure you’re not bringing up or blocking anything.