Who knows about stacked-block retaining walls?

[Sodo]

From my POV... I'm getting great input that is helping to move along.
What advice do you think I'm ignoring... that will doom my wall?

What I need is tiebacks,
The wall goes in tipped back at 1:6.
Would be nice to find a way to "qualify" that they'll keep the wall tipped back against the geotextile.

Also would be good to hear from someone who knows whether a geotextile layup can push a block wall out.
It's like a soil wall itself, 6 feet thick, and it's tipped "back" into the slope, perhaps 1:1 or 1:2.

 

[dstig1]

CurlyDave?!?! Man I haven't seen you on here for years! Good to see you back!

 

[ultrarunner]

I’ve checked a few times for Curly Dave and came up dry…

Nice to see you are among the living…

I miss your thought provoking tag line at the bottom of every post!

One for old times…

“The true delight is in the finding out rather than in the knowing”

Isaac Asimov

 

[lilranch2001]

From my POV... I'm getting great input that is helping to move along.
What advice do you think I'm ignoring... that will doom my wall?

What I need is tiebacks,
The wall goes in tipped back at 1/6.
Would be nice to find a way to "qualify" that they'll keep the wall tipped back against the geotextile.

Also would be good to hear from someone who knows whether a geotextile layup can push a block wall out.
It's like a soil wall itself, 6 feet thick.

I really didn’t mean to start an argument with you, I just worry about things, such as retaining walls and such.
But since you ask, I’m going to say what I can remember I’m not gonna go back to the whole thread and try to point out every detail but to start off with most everybody mentioned sand is a bad backfill, common sense tells us that sand drains well, but it really doesn’t. You seem to completely blow that off.
People mentioned that you need a drain at the bottom of the wall well finally you gave into that but you went with an inch and a quarter pipe typically a minimum size pipe for a bottom drain would be 3 inches I guess inch and a quarter is better than nothing But will do the job who knows .
You ask why put holes in the pipe and where to put them so people told you where to put them rather than put them top and bottom you put them on one side and then when your guys orientated the pipe they put it at the top so now you’re going to have water standing for an inch and a half Above where it should be at that’s going to create a problem at the base of your wall. Rather than spend five minutes and go in and double check the orientation of that pipe or had you just put holes top and bottom then would’ve been solved, at least in some fashion .
I’m pretty sure people mentioned that the way you were doing the fabric was incorrect, but I didn’t pay that much attention to it because I’m on my phone and it’s hard for me to see how the fabric was laid out so I won’t swear to the fact about the fabric, but it seems to me there was mention of the fabric that it should be redone.
And then there was something else at the end of this whole conversation that tripped my triggered to make the negative contents that I posted above this one, but I don’t recall what it is, it’s midnight almost and I’m tired and I’m ready for bed.

Like I said, maybe I’m all wrong and you’ll have a perfect wall forever and ever but it’s taller than typically should be especially with the less than ideal engineering that you’ve done

When I was doing my walls, I was going to do them myself as well as I mentioned earlier in a post and I decided not to but I had done a lot of research and I spoke to a lot of experts one in particular, was the wall engineer that works for the company. My son-in-law works for he does a lot of commercial retaining walls in commercial and schools, and I’ve never forget a statement he made to me saying if the wall is over 3 foot tall there is almost 0 tolerance for error on retaining walls.

 

[ultrarunner]

When building stacked walls my considerations are substrate, type of block and height.

The ground here is mostly serpentine rock that shatters when digging… made my job easier because I already had base material and backfill… 25 years without issue…

“A great many things are possible.” And to himself he added: But not practical“

Isaac Asimov

 

[Sodo]

OK, it's hard enough for me to re-read the whole 10 pages myself.
lilranch.....i consider this a discussion, argument has not entered my mind.
ideas, solutions come from discussion.

....I'll recap some of your concerns.

Tree removal is recommended.
I've wanted to take them out before the wall was even an idea.
I got a bid 7 years ago, $5,000 and $2000. So 2025 will be...... what, $8,000 and $3000?
I'll take the trees out later, if ever........or let someone else do it.
Would have been nice if someone did it 30 years ago when it was easy, before all the tree protection laws etc.

I have free-draining gravel behind the wall, from bottom to the top row.
My wall-builders said it was required too.

I put a 1.25 pipe in clean gravel at the bottom, with its slots on the bottom.
Wall builders rotated it to slots on top. It's buried now.
The water has to be one inch deep to get into the pipe, but water that gets in..... drains all the way to the outlet,
Rather than charging up the ground a foot downstream of its entry point.
There are pluses/minuses to each configuration.
I don't see one inch as a wall-killer.

12 inches up (per the diagram) there is a 3" corrugated pipe (in clean gravel) that's perforated on the bottom (and all around).

It would have been nice to put geotextile tails coming out from between my lifts,
to clamp between the block rows as tiebacks
But that's 20/20 hindsight, not possible to re-do.
And unnecessary per block mfr recommendations, 7 rows, 42" high can be free-stack.
I'm real happy with the upper wall.

I'm "hopeful" that the geotextile layup is self-compacted enough, because it's "sand".
It's creating "level land" where it was un-usable slope.
This is just for parking a car and a little yard, it's not a building site.
=====================

The lower wall is only 8 feet long but it's 4 rows higher than mfr recommendations for free-standing (11 rows, 66 inches).
Here, some geo-textile tails would've been useful.

A lot of my land has been been leveled over the years. It's steep.
In one area that I was digging in some fill I found lots of rebar, concrete rubble in the fill-dirt. The garage was built in 1978 (47 years), which suggests the fill was done around then. The buried rebar (in fill-dirt) was rusty, but #5 was still solid. #3s were getting down to about #2 ;-) .
Other areas, I dig into the original sand (on the steep slope) and just a foot down or so, the sand is dry even in the winter.
Anyway I have some examples of underground steel onsite, that I think are usable to assume underground lifetime.
I bet they last almost forever in sand - if the sand drains.

I'm hoping to lock tiebacks into sand though.
Steel doesn't lock into sand like it does in soil.
Plusses/minuses....sand requires a deadman...but sand doesn't rust the steel so bad.

I see some challenges that would be nice to discuss with others who have seen similar.
I do appreciate the critical thought, it keeps me on my toes.
Some things could be better but I don't see imminent failure.

=====================

I currently need ideas for tieback methods - that can be done before wed Feb12.

 

[lilranch2001]

Trees……..
I’m sure you have not even thought about the force those trees put on the whole structure, in a wind event……
2- 100 foot tall sails that transmit all those vibrations down to the root ball, as the root ball is becoming saturated at the same time.

You just have a whole lot of “maybe, ifs, hopefully that’s,” that if all work against you at once…….

All I can say is I hope you have Gods good Grace looking over your shoulder!
I know I have rarely temped God with so many challenges and got away with it

 

[Streetcar]

Can you put layers of geotextile behind your taller wall. Attach that to your anchors. If not put anchor in block with large washer to distribute load

 

[2manyrocks]

This thread started with what at first looked to be a simple problem, but one of the last photos shows a very complicated and large project that is very far along. In a perfect world, the drain and tie backs would have been installed in courses as the base was built up.

I'm the one who mentioned helical ties, but I have strong reservations that they are the solution at this stage of completion of the project. I just don't know what else to suggest to try to salvage this situation.

Will say, I too, have missed Curley Dave and it's great to see him back on TBN.

 

[Sodo]

Can you put layers of geotextile behind your taller wall. Attach that to your anchors. If not put anchor in block with large washer to distribute load

The 11th block will be 3ft from the geotextile lift. I don't think my geotex fabric will do 'much' in 3 feet. The hard plastic type would be better for this, I think ___IF____ it was soil. But the backfill will be sand then gravel.

================

My current plan, is to have 3 "weldable" blocks on row 6
and 3 more on row 10.

Then weld 5/8 rebar 'ties' from row 6&10...
to the (steel) tieback structure (proposal) which is a welded rebar rectangle frame.
Welding the ties from the blocks to the frame structure, before the backfill.

Unless someone has a better idea.
Understood it's difficult to fully get into "someone else's project".
I do have a couple creative friends who can do this, but they're preoccupied currently.
Wall builders return on Wed Feb12.

Haven't done anything on this yet, other than ordered 12 helical ties, which I don't know at this point, untested (by me) if they are going to "satisfy". I will need to extend them, to drive in much deeper than their 18 inches, more like 3 feet. They are thin steel, how long can they last? If they were coated thick with zinc..... that would help but I bet they're not. I bet they last only 10 years, and with luck, 20. And hope is they lock into the sand (which was not mechanically compacted) that has umpteen tons of sand pressure from above. I'm not real happy with them either, except that they hold things together as the whole pile settles. Thoughts and prayers.....

I have more faith in the longevity of fence T-posts. T-Posts cost the same as the helical anchors (appx $6 each), but are 6 feet long, epoxy-coated and much thicker, much more hopeful. How long do fence T-Posts survive soil contact? Someone on TBN must have a "real old fence" dating back to the beginning of T-Posts. The internets say they appeared in the '30s, becoming more common in 1950s, 60s. Does anyone have 50+ years old T-Posts?