Stone Retaining Wall

[pelli69]

I have been tasked to design a 2.5metre high retaining wall.
Trick is that the client wants to use 600mm high X 600mm wide X 1500mm long sandstone blocks cut from the excavation they have carried out on site. These blocks will be laid onto solid rock foundation.
I have designed timber, concrete and masonry retaining walls in the past but have never designed a sandstone block wall.
Does anyone know of any design guidelines/documents I can reference?

 

[msquared48]

They probably don't want to hear it, but I would construct an 11 foot high retaining wall of concrete and face it with the sandstone. Otherwise this will have to be a gravity wall with all of the dead load resistance coming from the sandstone itself. That's a lot to ask for an 11 foot high wall, and a lot of sandstone.

Mike McCann
MMC Engineering

 

[bridgebuster]

Take a look at the attached drawing. It's from 1913 - I think it was Mike's first assignment - plenty of 100 y/o stone walls built from that drawing still standing here - good work Mike.

Or Google this
ROCKERY DESIGN AND CONSTRUCTION GUIDELINES
Publication No. FHWA-CFL/TD-06-006

Designing one is a bit of a pain in the @$$. You size your stones for each layer so that the eccentricity is within the middle 1/3 of the stone width, and check sliding resistance layer by layer.

 

[msquared48]

You should talk. You're the one with the detail!

I've added it to my collection too. Thanks.

Mike McCann
MMC Engineering

 

[dhengr]

Pelli69:
I would want the mating surfaces on the blocks to be fairly well dressed, so they fit together well and provide lots of frictional surface contact. How are these blocks being mined and readied for use? I would leave the exposed faces as natural as possible. I would like the bottom couple courses to be 24" high, maybe 36 + deep/or wider and 5' long. Can they handle the 5' long pieces without them breaking in the middle? I would certainly build this wall in a running bond pattern. It is a gravity wall in terms of its stability, but it is also a flexible wall system w.r.t. some movement, so prepare the base well. I think Bridgebuster’s publication on ‘Rockery Design’ talks about this; also look at some of the literature from suppliers of the large precast and keyed conc. block retaining walls. They have some design aids which might be edifying. VERSA-LOK and ROCKWOOD come to mind. I would put a foot or two of well draining granular fill behind the wall and a geotextile fabric filter, in a vert. plane, btwn. the granular fill and the retained soil; along with a drain tile or some such at the footing level. I would fill behind the wall as I built it up. I would batter the wall back several inches with each new course of blocks. How well does this sand stone weather, particularly w.r.t. rain water and freeze/thaw?

 

[Archie264]

>>>You should talk. You're the one with the detail! rofl

I've added it to my collection too. Thanks.<<<

Yep, I've got it too, now.

 

[bridgebuster]

Guys,

I'm glad you found the drawing helpful. I have tons of stuff (figuratively speaking, since I scanned most of my paper files). Unfortunately, many from the younger generation don't see an value in these things.

Have a good weekend.

 

[oldestguy]

The client wants what has been done for years at Dubuque, IA. those are nothing special, but they are sloped back maybe 10 degrees or so. This would be similar to what is provided commercially by those with pre-cast concrete blocks, sometimes along with reinforcing of the earth backfill for the MSE walls. I had one built out of concrete blocks 2x2x4 ft. made from left over ready-mix concrete. I used reinforcing, but a gravity wall, when designed per the usual checks on stability will work. The only question i would have is the long term integrity of sandstone. Some sandstone will fall apart with time.

 

[CELinOttawa]

Bridge Buster:

Count me in as one of the younger generation who DOES value these, and has made a point of collecting all that I can... If you have copious amounts of scanned files, I would be eternally grateful to be able to get my hands on anything you'd be willing to share.

I haven't a ton to share in return, but I have a good deal of similar literature thanks to my Father and Grand-Father, as well as my own persistent collecting. I would happily post you an external hard drive with all that I have for your perusal (and use), and pay for the return postage for you to send me back what you are willing to share.

Regardless of my proposal above, if you'd consider a swap of any kind please contact me on "m (·space·) quinn (/at/) celottawa (-dot-) ca", no quotation marks. And thanks, this is already an excellent addition to the library!

Cheers,

CEL

 

[pelli69]

Thank you all for you input

 

[SLTA]

I have several old books, like turn of the 20th century, that are super-helpful to know how systems were constructed back then. I too would happily take your old books/papers. Or, you could talk to any of the structural historic preservation grad programs. I know UVM has one, maybe Texas, and there are several others.

 

[EngInternational]

They probably don't want to hear it, but I would construct an 11 foot high retaining wall of concrete and face it with the sandstone. Otherwise this will have to be a gravity wall with all of the dead load resistance coming from the sandstone itself. That's a lot to ask for an 11 foot high wall, and a lot of sandstone.

Heed these words. This is the best solution.


Note that rockery guidelines advise that the long side of the boulder be placed perpendicular to the run of the wall. Therefore, you may want to check if you even have enough material on site.

If you do design the wall as a rockery, I'd be very interested in discussing your analysis methodology for a wall of this height. When I reviewed a wall twice as high (yes...twice...), overturning and sliding needed to be checked at each lift of stone, not just at the bottom of the wall. Understanding the line of thrust is critical here. The drainage system must be designed very well too because if the walls are tilted back, the wall will collect the rain water.

 

[SteelPE]

Meant to post this a while ago but forgot. This link has some pretty good information in the design of Rockery Walls:

http://www.cflhd.gov/programs/techD...ries/documents/01_Rockery_Entire_Document.pdf

 

[RHTPE]

I'm in agreement with Mike & EngInternational. Some consideration that I feel are essential:

- How critical is this wall to other structures on the site should it fail?
- If the life span of the sandstone turns out to be very short, how will the wall be repaired or replaced?

I was involved with some rehab work on an 1870s 2-story brick & timber dorm-style building with a rubble foundation. The foundation was faced with what was (at the time of construction) cut stone blocks on the order of 8-10" thick, 12-16" tall, and anywhere from 24" to 8' long. Turns out the "cut stone" was actually a sedimentary rock that did not fare well over the 140 years it was exposed to the upstate NY weather - much crumbled into what appears to be processed gravel. The challenge for this project was that the watertable stone and 1-1/2 wythes of structural brick above were supported by this stone facing.

I would think twice about using any sedimentary rock as the principle structural element in a retaining wall.

Ralph
Structures Consulting
Northeast USA