Retaining walls-suggestions???

[Anonymous Poster]

Hi all: Will be putting in several hundred feet of retaining walls next year toward the goal of leveling some property that currently has a 1:10 - 1:12 (more or less) slope. Max height of wall probably 6' - 7' down to 2' or so above current grade. Current plan is to use telephone poles (which I can get free for the hauling) buried vertically 2' - 3' deep against which the ground (upper side) is pressing. Because the poles are not a solid piece wall (as a concrete/block, etc. would be) I don't believe drains would be needed running behind the wall (although I might need to dump some gravel for drainage through the poles making up the wall. Simple and relatively painless. Dig a trench, place poles cut to length, pack (and compact) lower side of wall to hold poles in place, then dump dirt (etc) on the "upper" side of the wall. So . . . what do you folks think? Am I missing something? Any experienced suggestions most appreciated. John

 

[Hoeman00]

The depth should be more like 4'+ because of
pressure on posts and since they are round
and not tied together they could push into
down slope side of trench.
Putting an angle on the trench back toward
slope will help to.
In the midwest the get below the frost
level need to go 3' .

 

[MDSteve]

The last retaining wall I built was 30' long and 10' at the highest point. All the posts were 6X6x16. We tried to get all our holes 5' deep. If I had to do it again I would have used a larger auger. I used a 9 and then a 12 but it seemed that after we dug out all the rocks the holes were about 18-24 inches wide. By the way we put 8X8 railroad ties in for the actual wall and used the PT 6x6's for the post.

Steve

 

[JJT]

I recommend tieing the poles together with half inch rebar or half inch threaded rod every 4 feet, with a few pole spikes between the rod.

Also don't forget to add a deadman every 8 - 12 feet linear feet and every 3 - 5 courses of poles.

 

[Anonymous Poster]

Definitely deeper on the foundation, at least 4 feet. All of the pole tops will need to be tied together, poles do not stay straight by themselves, the wires hold them straingt.
You need to provide drainage, both behind the wall and at the base of the poles for maximum life. Frost behind a retaining wall exerts tremendous pressure against the wall.
Most Important, you need to anchor the top of the wall back into the fill every few feet, or the wall won't withstand the pressure.

 

[rdbrumfield]

For sure on using drain rock for the full lingth of the wall with drain pipe, Also use a filter fabric against the dirt wall on the uphill side to keep the drain from becoming contaminated, you won't be sorry.

 

[Anonymous Poster]

Hi,

Are you going to put up some kind of rail to help prevent the possibility of someone walking off the wall and breaking their neck?

I have a short section [80 feet maybe] of what used to be a drop off above my pond, and I ended up tapering it at about a 45 degree angle, thinking it better to have something to roll/slide down rather than the sudden drop off...that is on foot, not on the tractor! /w3tcompact/icons/smile.gif...I did not have any rail or other warning that it was there, and while in daytime it was easily seen, at night is was not.

That taper ends about 15 feet from the pond, and there is a flat area around the pond where I can drive the tractor, or walk/whatever.

Just bringing this up as an alternative...if you actually need a wall that is one thing. If you can get by without a wall, you might be better off in the long run without one.

I hope to get something growing on that slope that I don't have to cut or maintain much...

Just a couple alternative thoughts.../w3tcompact/icons/smile.gif

Bill in Pgh, PA

 

[Green_in_MI]

I was going to initially suggest that you hire a engineer for an hours worth of advice. However, the suggestions in the responses do cover most of what one would tell you. I would reitirate a few things. Drainage is paramount. Increase your depth for posts. Use the deadmans back into the hill. Read some books on the subject. Get the advice of an engineer. Several hundred feet of retaining wall is obviously a big project and costly. Professional advice will be only a small cost of a successful project.

BTW, I am real impressed with the advice by responders. Sounds like people who are used to doing major projects with tractors and stuff.

 

[jray]

Maybe Think about the fiber barrier you can put between the poles and the backfill inorder to prevent any dirt from washing through the wall when it rains. I got some at LOWES and it works great. My project was nowhere close to your size but it might prevent washout.. Jray

 

[Darren]

Drainage helps but if you have a clay backfill, you'll have problems. Water doesn't flow easily through clay. Of all backfill materials clay will produce the highest active pressure on the wall.

The best backfill material is sand (least pressure on the wall). If you use geotextile as a wrapper for sand backfill, the fabric will prevent soil from infiltrating and blocking the sand and keep the sand in place.

The most consistent problem I've seen in retaining wall construction is the backfill.