Block wall falls on 320 cat

[minimax]

This is what happens when you mix somebody that does not know what there doing and a rented 320 trackhoe!!!
2679

2680

2681
minimax

[CascadeScaper]

I've been to that site, it's crazy steep behind the wall, the hill just keeps going up. They really designed the house wrong, it should have been closer to the road, and the wall should have been terraced and better engineered. Morons.

[Ford LT-9000]

For a situation like that that bank should have been benched or a massive poured concrete wall installed with heavy rebar.

Lock blocks have their place but nothing beats a formed concrete wall you form butresses onto it to brace the wall to keep the forces from pushing it over.

[Squizzy246B]

Lock blocks have their place but nothing beats a formed concrete wall you form butresses onto it to brace the wall to keep the forces from pushing it over.

Tell me more about "Lock Blocks"..??? are they solid?

[tylermckee]

Tell me more about "Lock Blocks"..??? are they solid?

Just sold concrete blocks, leftovers from cement trucks. ecology blocks. make a pretty good wall, just ugly as the a bucket of buttholes.

[CascadeScaper]

Anyone know the estimated weight of those things? I've never had to place any, but they look pretty heavy. 3,000 pounds? They do make a good wall given you know how to build a wall. Just because they go together easy don't mean building the wall itself is easy. I've seen plenty of eco-block walls bow out and tip over, even on the eastside of the state where rainfall is much less.

[minimax]

The 2'x2'x6 are 3700 lb, 2.5'x2.5'x5' are 4700 lb.that 320 had 13 blocks on top of it!!:eek:

minimax

[digger242j]

So, what are the details--what made the wall fall down, before it was even finished?

[Ford LT-9000]

I like Tyler's comment on lock blocks:lmao

With lock blocks you need to have so much degree's rack back for the height of the block. A wall that tall would need a good tilt back against the bank it would probably require a buttress wall and a concrete foundation to sit on.

Lock blocks are a pain to work with as it takes allot of prep work to build a proper wall. A formed concrete wall might cost more but its stronger your not relying on gravity like lock blocks.

We have options for split faced blocks they look a little better but not much.

The standard block is 3000lbs they are making heavier ones now they are 4000lbs or something like that. Have to be a little carefull handling them you bump them around chips and chunks break off of them. There is a galvinized wire loop on top its what you pick them up from if you get too rough the damn wire pulls out :cussing

Anything over 48"s has to be engineered and the engineer draws up the block plan on how things should be laid out.

[Squizzy246B]

So are these blocks moratered or tied together? or is it just a simple tongue and groove.

By the look of it if the machine was backfilling and knocked some of the top blocks it would all come tumbling down.

[minimax]

The guy that puy the wall up owned a landscape com. and rented that machine and told the owner of the lot that he had done many walls, the wall was engineered but the guy can't read plans, the wall called for 1 to 6 tip back but the guy went straight up 28' feet and did not back fill as he went up but went he got to the top and because there was no tip back it took way to much back fill put in and the wheigh of the backfill compacing it started to push the bottom of the out so they were stacking blocks end to end in from to try and stop the wall from moving, the guy's wife had showed up with lunch when the wall came over on the machine,It took a 225 ton crawer crane to get the 320 out!!

minimax

[minimax]

Squizzy,they are tongue and groove.

minimax

[Steve Frazier]

In NY, any retaining wall over 4' must be engineered, apparently this one wasn't. They are fortunate it failed during construction instead of down the road when the homeowners children could have been playing in the yard. On any retaining wall like tis, the bottom course or 2 are supposed to be below grade to keep the bottom from kicking out. If a gravity style wall is built to design, they function well. Buttresses are not necessary if the wall is properly designed.

[Squizzy246B]

Thanks Minimax. But are you saying that that wall has no backers..backing blocks behind the lower section to increase the mass??

Our mass wall are essentially a pyramid cut in half....with the mass of the wall equivalent or exceeding the weight of the backslope mass plus additional surcharge.

To mind that arrangement, as it appears, should have had a vertical division of landscape or filter fabric with clean sand behind and aggregate in front. This would have been a PITA to install but reduces the load on the wall.

If that wall has no backing then it should have had back ties or Geogrid.:ban :ban :ban

I'm hoping that at least nobody was hurt.

[digger242j]

Thanks, Minmax. That explains a lot.

Even stacking blocks in front of it wasn't the solution. It had to come down, one way or another... :rolleyes:

[minimax]

the wall was engineered but put up wrong! the wall had no backers, tie backs,geogrid,etc bad from the get go!!

minimax

[Squizzy246B]

Thanks again Minimax, thats a real shame. There has been several mass walls fracture badly in my state recently and a couple of those made it to court....I was called up on one as an expert witness for the prosecution.

The knee jerk reaction has been to change and over design the walls instead of looking at the workmanship. Our mass walls are already so far over the top that it can usually only be workmanship (read poor compaction 9 times out of 10) that causes them to have problems. Given that, a well designed mass wall can have defects/fractures all through it and it will not fail/fall catastrophically because of the backslope and the shear mass. Looks like this guy lacked a good understanding of the real basics that go to making up a wall.

What gets me is the backfill area looks to be 2' to 3' wide in what I can see...thats a lot of tons of aggregate...and like Steve says the first course does not seem to be buried below grade.

I hope it was only the 320 that got hurt.

Here is pic of what I mean by backers being installed behind the face:

[Nac]

I belive that usally 1 block is buried(min.) for every 8 that goes up. They make a similar block I cant remember the name of them but they have a speical channel in them that receives geogrid and epoxy coted rebar to reinforce the wall just like smaller SRW walls.

[Ford LT-9000]

When ever block walls are done here its preparation and more preparation taking time to make sure the first course of blocks is perfect using the laser level.

The last wall done here the guys got one row in put the drainage in then put the backfill in took the jumping jack packed the material down. The continued with each row.

We wouldn't tempt installing a 28 foot tall block wall it would most definatly been benched or the bank behind it dug out.

[minimax]

Yes no one got hurt,2' to 3' of over cut would not of been that bad but they over cut the hill by 6' to 8' feet,look on the 2nd pic. and see the end of the blocks are 2'x2' you can see how much over cut there is!

minimax

[Dusty]

scarry stuff

[CascadeScaper]

Next time I'm up that way, I'll check out the site and see how it finally got done. Maybe I'll get some pics. It was a challenging site to start with and the lack of experience really made it worse.