Who knows about stacked-block retaining walls?

[Sodo]

Here's what my guy said.
On your hillside it's not going to be flooded behind the wall.
You will have water coming down from above at one or two places.
If you put holes down it will distribute water over the whole base.
If you put holes up it will carry that water out.

your going to have an extra 1 1/4 of water before your drain pipe starts evacuating.

If the holes are on top, the water level has to be at the top of the pipe to drain. I've always used drain pipe with holes all around.

Putting the holes at the top creates a pond at the bottom of your wall. Basically, you have created a dam that will allow the water to remain there and soak into the base of the retaining wall.

I set it holes-down and he turned it holes up.
I was tempted to tell him what I had read "on the internet....." but decided not to because thats all I had.
I've found fantastic info on the internet opposing what the experienced practitioner does,
.....and I bet we all have.
I understand the that the internet is wrong often.

Anyway I'm curious what you guys think of his POV.
He said the water is all coming from above the holes,
in the areas where it's coming to the pipe.

Well anyway the pipe daylights.
If water is above the slots anywhere along the pipe, its a closed-bottom trough that will run any water out the visible end.
I suspect the gravel bed will be "open" for many years and by the time even one drip runs out of the pipe.... I will have long forgotten all about it.

 

[Sodo]

Upper wall is done, ready to remove that last form-board and add the topsoil embankment.
That form board is 4 x 12 x 22 ft long.
Note the gravel waterfall, you can see it in the next pic.

In the coming weeks I'll cover that slope with dark topsoil which will grow stuff fast.

Lower wall is started.
They poured a concrete footing about 18" deep to support the left end.
This wall will be 11 blocks high, coming up to the level of the deck
at the bottom of the stairs.
They said it should probably have 3 drainpipes and should have tiebacks but didn't have any ideas.
that black pipe is temporarily accepting the driveway and downspout water outlet.
A tight PVC pipe will be attached there.

Its up to me to figure out a way to anchor tiebacks into the geotex lifts....
I have several days before the wall builders return.

 

[2manyrocks]

Every picture you add to this thread shows much more layers of complexity to this project.

I disagree with the installer. Water tends to go to the lowest point in a trench, then fills the pipe to carry it away.

If you look at the pictures of how they are attempting to restore stability to the sections of I-40 in western NC that washed away during Hurricane Helene, they are installing helical anchors into the slope. That might be something for you to consider.

 

[Sodo]

Clever. It would be cool if you could do a video

OK.....here's the difference between the engineer pre-planning with available tools...
and the experienced wall builders.
They didn't mind my soft-jaws method for the 1st wall,
I think because it was an opportunity to flog their phones while I did the 'work' with the mini-ex.

For the lower wall they just set a 2x12 at the proper angle and slid the blocks down the board.
The angle they set controls the speed.
It was much faster and safer than my mini-ex-soft-jaws method.
I think perhaps 3x or 4x faster. Maybe 5x.

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

Yeah the gravel bed below the blocks will carry the water for many years.
His theory won't amount to anything until the gravel bed plugs with silt (and rises an inch or so to get to the slots).
I'll probably never see a drip from the pipe and if I do, that means there's a significant amount of water coming "from somewhere" that should be dealt with.
I suppose it's like "an indicator".

 

[2manyrocks]

Having a guy to feed the block and another guy to catch it at the end of the ramp is different than working solo. I’ve roped stones down a ramp before. Not fun.

 

[Sodo]

Yeah solo.....no sh*t ! Forgot I was preparing for solo...
SO glad I didn't even start building this wall solo.
I'm too old for this.
I can do it but it's just dumb.
I could put me under 6 months of bed-rest, and perhaps never fully recovering.

Compacting with a track machine next to not doing anything.

Agreed, but that's all I've got. Trackhoe seems to compress the moist sand about 2 inches deep. But it kinda vibrates under the track-rollers, and the track lugs "press in" on successive passes.
The geotex does get tight at the nose with several passes..
There is the successive SAND tonnage of each lift ontop of the one below.

On the 2 top lifts I used the B3030 tractor with a full bucket load, which is extended pretty far in front of the front wheels. The small wheels press a lot harder, and "roll into" the soft material, making much deeper ruts than the excav tracks.

I will record laser-level elevations to monitor what's happening over the years.
It doesn't have to support a cement truck, but I bet it will in a couple seasons.
Even so, it's a tight parking place for a small car. My F150 barely fits.
But fairly soon it will have some F450 sized dumpers backing in there when I start to push topsoil over the bank.

OK lets say I gained 400SF of level land..... at great effort.
It's essential because this little house has no "parking spot" and will be much more rentable with a parking space.

So,,,,,, does anyone have wild guesses how much this project would bid out "commercially"? Engineering, materials, and everything? I kinda think it's would be 5x the cost of a retaining wall rebuilt with existing rocks.....

 

[lilranch2001]

View attachment 2643127

Perforated a 1 1/4 for the bottom course.
View attachment 2643128
Ok it’s started.

My guy said he needs to work with his experienced partner. He said there’s too much to learn and much too slow if I was his helper. So it’s gonna cost more per day but I’m sure, less overall.

Watching them set the first course I can see it would have been a crappy wall if I was doing it. Lots of setting, tamping, resetting the first course. Each block gets moves several times. Re-packed, re-set, re-leveled. Looks strenuous.

Best money I have ever spent paying someone to build my ~100 feet of walls, like you said, starter course has to be dead nuts on, or you will have a f’ed up wall in no time.

You may have saved yourself with that 1 1/4 drainage as long as it doesn’t plug up

 

[lilranch2001]

View attachment 2651749
I made this image with photoshop from an install doc posted by airbiscuit.
I was real happy aircommuter asked for it - because then I had a diagram for the wall builders.
I was ready to do it all by armwaving.
A drawing is much better.

The height of the standing blocks is the final 42".
I have not purchased any top-caps.
I decided to "conserve gravel" a bit because I have a sand mine "on-site".

View attachment 2651615
Here it is at the end of the 1st day.
5 blocks up.
You can see the plywood separator between the gravel and the (packed) sand.
No fabric between the gravel and sand.
I'll put a level fabric sheet ontop below the topsoil.

View attachment 2651746
I cannot believe the cost of gravel here.
The economics of scarcity makes sense,
but gravel pricing seems controlled by a local cartel.


Eddie can you explain why? I told the builders that the holes go down, but he said that doesn't make sense.
He turned them upward and I didn't protest because what he said made more sense than my foggy memory.
I remember your mention for sure.
Can you remember the reason?

I’ve learned the hard way, bad choices always bite me in the butt, now you will have almost a 2” layer of water that will not tend to drain…

 

[Sodo]

they are installing helical anchors into the slope. That might be something for you to consider.

I ordered some small helical anchors.
I'll weld them to rebar to lengthen them,
and see how far they'll screw into the sand.
I'm guessing they screw right in.

I wonder how to 'qualify' them.
The blocks mfrs say beyond 7 rows (7x6=42"), anchors are needed.
This wall will be 4 rows past the limit, 11 rows.
But it's only about 8 feet long.

I'll pound a fence t-post in with my gas-powered post driver (see how it feels.
They're epoxy-coated and seem to hold fences up for awhile in the ground.
6ft post costs about the same as a helical anchor, but the helical anchor has a 3 inch 'deadman' on the end.

Here's a proposal for the helical anchors.
Put the anchors in and weld them together.
Then attach to the blocks somehow.

I need some tiebacks in place, ready to attach to some blocks by Wed feb12.

I'm thinking to attach to row 6 and row 10 (of 11 rows).

 

[lilranch2001]

I hate to be a Debby downer, but you ask for advise from TBNers and then go ahead and ignore most of the advise offered up, and proceed mostly the way you had planned before most of the advise.

I hope you are luckier than I feel I would have been following the path you have taken!

Ive seen walls that have collapsed, and to be real honest, it’s never pretty