Wood retaining wall 2

[bstar333]

Hello all. Stumbled on this forum, hope someone can help.
Going to build a retaining wall with 6x6 lumber. It will be approx 8' high and it's on the side of a slope.
Looking for the best way to do this. Thought of splitting it into 2 4' sections.
The second section pretty much resting on a 6x6 coming out of the first section.
Also thought that in addition to the sleepers/deadmen, using a geotextile (see yellow in picture) sandwiched
onto the back of the wall and then run within the backfill. The geotextile isn't cheap, so I'm not sure if this
will even serve a purpose.

 

[bstar333]

I do want to mention that in my picture, I have used what appear to be 12"x12" logs! They are 6x6, so there aren't enough depicted

 

[concretemasonry]

That looks like an unplanned failure. It is an all too common way out of trying to build a high wall by using set-back distances that are not sufficient and very little anchorage back into stable soil. - The entire "structure" is just asking to slide down the slope.

I think a good engineer and a little soil sampling will give you something that would be legal and approved.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[RFreund]

My first choice would be a segmental retaining wall (precast block system) such as Keystone, Allan Block, Versa Lock, Anchor, etc.

EIT

http://www.HowToEngineer.com

 

[oldestguy]

Provide more data. What type of soil is in that slope? What is the backfill proposed? Any water present in that bank? What purpose for the wall? What will sit on top?

Off hand, the only geotech layer you show that would appear to have some merit is the top layers and even then maybe too short.

If that drawing is to scale, I see the slope at 30 degrees to the horizontal, which is just "safe" for loose sand. Adding any wall is likely to fail, with that assumption..

 

[PEinc]

In addition, fill should not be placed on that existing slope without some horizontal benching to prevent the fill from sliding down.

http://www.PeirceEngineering.com

 

[RHTPE]

If it were me, I would NOT do a timber wall. I have a 20+ year old wall that has deteriorated almost to ground level on the face side. Simply put, wood will rot over time, no matter what kind of "preservative" is used. What kind of problems will you leave the next owner?

If nothing else, use a segmental precast wall with properly designed geotextile grid holding it in place. It is more than worth the investment in the long run.

Timber walls are good only for low height landscape features that can easily (relatively speaking) be replaced in future years.

Just MHO.

Ralph
Structures Consulting
Northeast USA

 

[Ron]

Ralph....exactly!

 

[cvg]

an 8 foot high retaining wall will almost certainly require a permit. have you run this idea past your building dept yet?

 

[msquared48]

Well, if you are in a dry environment, which I am not mind you, a wood wall could work for 30 years or better. Mine, 5 feet high, has held for 30 years, but is of much different construction than you show.

I used 4X6 PT posts at 5 foot centers embedded 2 feet into cementious sand (an 8" power auger would hardly touch it), sll in a concrete filled hole, then spanned PT 2X6's on the backside for a temporary wall. The next year I came back and strung some horizontal and vertical rebar between the posts and infilled with a 5.5" thick concrete wall, with a small 2 foot toe formed into my driveway (do you think that helped?). The posts are retaining some soil load from the concrete wall, but not all of it by any means. After 30 years, the posts are are still structurally sound though.

I would definitely step the wall, regardless what solution you use. If you decide to use pole footings, you will need to go deeper due to the downslope.

Mike McCann, PE, SE