Retaining Wall Failure

[Hay Dude]

We have a whole town of toppling walls. Mostly built in the 1700’s
The thing that gets them here isnt lack of pipe, aggregates or geotextile fabric or whatever.
Around here what topples walls are trees left to grow and their massive roots take down the walls.
Ones built 300 years ago here are still standing, IF the trees are kept away.

 

[Rustyiron]

^^ That's a dilemma. Probably both the trees and the walls are valuable historic items from the past and both worth preserving.

 

[Hay Dude]

Our community was planted with Kentucky Coffee trees 300 years ago. They are slowly dying off, being hit by lightning or have grown so close to our old roads they have to be taken down.

 

[fishdrivel]

You need a geotechnical engineer to review wall. I have seen certified installers, but designers are professional engineers

If you have an Engineer that particularly versed in retaining walls.
I have more retaining wall design experience than most engineers.
If I have a situation worthy of hiring a design engineer, I would like to know that he has experience in walls of that stature.

Part of my job working for the US Government was to review drawings before they go to bid.
Often they failed constructability review. I once reviewed a retaining wall drawing in Okinawa and my review concluded with report to my Colonel that it was not a matter of if it would fail but a matter of when.

Most retaing wall products are pre-engineered for standard production. The problem happens ofter that standard engineering is being used on a non-standard installation.
Examples: building a wall with a steep slope above it, walls that will have vehicles or other loads, barns and other structures, bad soil conditions, water, trees, etc. There are an almost unlimited number of problems you can encounter. I have reviewed projects that cannot and have not been constructed.

 

[ultrarunner]

I was told by an engineer that designs fixes is the good thing is most of the time the blocks can be used again... or even sold.

The person said it all starts from the ground up with a soil report...

 

[fishdrivel]

I was told by an engineer that designs fixes is the good thing is most of the time the blocks can be used again... or even sold.

The person said it all starts from the ground up with a soil report...

Many contracts call for "all new materials"

 

[Streetcar]

I was told by an engineer that designs fixes is the good thing is most of the time the blocks can be used again... or even sold.

The person said it all starts from the ground up with a soil report...

I have had retaining wall stolen for reuse of the blocks. Solution was to glue blocks together for top two rows

 

[ultrarunner]

Seen that happen locally and another lost an entire brand new sod lawn.

A friend scored an entire wall free for the taking... he heard about it from a contactor doubling the size of a home and the wall no longer needed...

Once the first course is properly placed it goes together pretty fast and for low walls not permit required...

 

[Streetcar]

If you have an Engineer that particularly versed in retaining walls.
I have more retaining wall design experience than most engineers.
If I have a situation worthy of hiring a design engineer, I would like to know that he has experience in walls of that stature.

Part of my job working for the US Government was to review drawings before they go to bid.
Often they failed constructability review. I once reviewed a retaining wall drawing in Okinawa and my review concluded with report to my Colonel that it was not a matter of if it would fail but a matter of when.

Most retaing wall products are pre-engineered for standard production. The problem happens ofter that standard engineering is being used on a non-standard installation.
Examples: building a wall with a steep slope above it, walls that will have vehicles or other loads, barns and other structures, bad soil conditions, water, trees, etc. There are an almost unlimited number of problems you can encounter. I have reviewed projects that cannot and have not been constructed.

Every block retaining wall ,I have worked with ,is designed to be four feet or less in height without modifications. The wall requires minimum bearing strength of original ground.
surcharge, bearing ,rotation and overturning are typically included in any retaining wall design.
fishdrivel, can I ask how you received your design experience?

 

[fishdrivel]

Every block retaining wall ,I have worked with ,is designed to be four feet or less in height without modifications. The wall requires minimum bearing strength of original ground.
surcharge, bearing ,rotation and overturning are typically included in any retaining wall design.
fishdrivel, can I ask how you received your design experience?

NCMI training, on the job, private study, working with many engineers.

 

[meackerman]

been working for a civil engineering company for 25 years now...not all engineers know what they are doing even when working in their field specialty.

And no I'm not a civil engineer, I just write the software they use.

I asked a couple of the engineers that I work for about something unrelated to our field of work (water resource management) and they all said they had a basic understanding so they could tell me the basics, but I needed to consult an engineer that specialized in that field for detailed, useful information.

 

[marhar]

I have always wondered why tall walls do not have rebar and concrete poured into the block plus lots of "dead men"

If it is only about cost, it would have been cheaper to do it right the first time.

 

[fishdrivel]

I have always wondered why tall walls do not have rebar and concrete poured into the block plus lots of "dead men" View attachment 728667

If it is only about cost, it would have been cheaper to do it right the first time.

Block with rebar and concrete still needs engineering - and they still need proper installation to that engineering.

I have seen many, many block walls fail.
I have seen and built very high segmental retaining walls in earthquake country, used as bulkheads at shore, and other difficult situations. They are usually stronger than block walls when properly designed and constructed.

see post #12

 

[Streetcar]

The high block walls are used to hold the reinforce granular material in place. Different locations have different solutions that work best snd cheapest.
The original post wall appears to have failed through erosion.

 

[Cameron Smith]

I'm a retired supervising civil engineer and I have a few thoughts about hiring a contractor. The normal method is to hire the low bidder but the european method is a better way to be sure of getting it done right. Depending on the number of bidders of course, throw out the highest and lowest bids, average the ones that are left and go with the one closest to the average. This pretty well assures you that the job will be done right (but have an inspector on hand as much as possible) for a price that is fair. Remember that a contractor is entitled to a profit and if he is good, you want him to stay in business to do your NEXT project! Low bidding invites shortcuts.

 

[MoMower]

Had a customer call for help this past year. Found this

Wall is about 12’ high. That is their garage that they had built/attached to the house above.

Cost for this wall and another built by the same contractor was about half of what I would’ve expected….there’s the answer as to why.

This is outside my scope of work, so I passed. I’m not a wall guy but I have some knowledge, zero drainage, zero geogrid, not enough rock behind. No engineer involved.

 

[deezler]

Dang, that original wall looks to be quite poorly built. I don't see any pins locking blocks together, geotextile fabric or other strong-men back into the hillside, drain tile and gravel behind it, or anything. Just a dry stack of blocks made way taller than it could handle. What a waste.

 

[marhar]

Had a customer call for help this past year. Found this

View attachment 731971

Wall is about 12’ high. That is their garage that they had built/attached to the house above.

Cost for this wall and another built by the same contractor was about half of what I would’ve expected….there’s the answer as to why.

This is outside my scope of work, so I passed. I’m not a wall guy but I have some knowledge, zero drainage, zero geogrid, not enough rock behind. No engineer involved.

I am curious, is there a general rule for how close a building can be built to a retaining wall? Even if the wall would have been well built it seems that the building it too close to the wall.

Attached is a picture tall retaining wall close to Charlotte NC. The builder used this wall to develop land that was in a high traffic area and also in a ravine. The buildings were condemned at the time, I do not know their status today.

 

[MoMower]

I am curious, is there a general rule for how close a building can be built to a retaining wall? Even if the wall would have been well built it seems that the building it too close to the wall.

Attached is a picture tall retaining wall close to Charlotte NC. The builder used this wall to develop land that was in a high traffic area and also in a ravine. The buildings were condemned at the time, I do not know their status today.View attachment 731979

I don’t know, but I know enough that I advised the customer that she should direct that question to an engineer as it did seem to be to close to the building, on top of all the other failings.

 

[marhar]

Dang, that original wall looks to be quite poorly built. I don't see any pins locking blocks together, geotextile fabric or other strong-men back into the hillside, drain tile and gravel behind it, or anything. Just a dry stack of blocks made way taller than it could handle. What a waste.

Agreed. I am not an engineer! BUT it seems like a few strong-men or dead-men would have helped. With the labor and cost of block it seems like one could justify placing rebar and pouring concrete as insurance.

I know a state building inspector (he was an engineer) that poured a wide deep foundation with rebar standing out of the foundation. He stacked cinder block and then and filled with concrete reinforced with rebar. After the wall was complete he had a rock veneer placed on the front and backfilled with red clay soil.