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Block wall falling

Block wall falling

(OP)
Hello everyone,
I would like to get your onion and help on this matter. I am being asked to fix this problem which is not my specialty.

A storage building made of 2' x 2' x 6' concrete blocks stack on top of each other and a fabric enclosure sat on top.

The wall is made of four course and there is no reinforcement.
The only sit on very small keys along the blocks.

The back wall is becoming mis-aligned and the top blocks overturning.
The owner has put some steel bracing and seems is not solving the problem

I don't know where to start, to me is not a solid gravity wall because is not one piece but stack of loose blocks
What the solution and direction appreciated

Any reference - sample old calcs?

RE: Block wall falling

There are a few threads on this in here already.

You have to check for sliding at each block course. I would likely be neglecting the keys (depending on how small is small) and designing around that.

What is being stored in this enclosure?

RE: Block wall falling

SKJ -

The first thing to do is recognize that the "structure" is not suitable for an engineer to analyze and give a clean, short and terse report that has any real authority.

Possibly more information on the future use would shed some light on the question.

It is probably just a building that was built using some available materials and methods. - the "roof" probably of tubing and a fabric offers no stability and questionable transfer of vertical and horizontal loads. - It seems it is just a gravity wall with a temporary weather enclosure added.

The basic concept of using massive, heavy concrete or stone block has been used for decades on many more substantial buildings. There are thousands of 4 to 7 story buildings (apartment and office) performing well in eastern Europe that are over 50 years old that were built on a foundation of 1Mx1Mx2M cast concrete blocks with no keys, no mortar or locking mechanism for shear resistance. There were no poured in place concrete footings because of available products and performance of previous structures, so bedding on soil was shown to be adequate. - Gravity and shear friction are very useful.

It seems that the portion of the structure has problems that are applying some lateral loads through the years that come and go and change with the season.


Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

RE: Block wall falling

Being a soils guy, I would be asking if the blocks are moving/tilting due to soil settlement or shearing issues. 6 feet is not very high. What is being stored within the structure?

RE: Block wall falling

Why is this post here a second time? It is not a building, but a form of retaining wall retaining sand for road salted sand. I suggest the managers delete this post, since it was well covered before.

RE: Block wall falling

(OP)
The problem is not definitely the settlement issue since it is sitting on a 12" reinforced concrete slab.
The material stored is gypsum for people asked me what's the material.

For people who say this problem was mentioned by others or past threads please refer me to those threads. It's easy to just say well in past this issue was stated.

If I did not need your opinion and if I knew the solution I would not post it here.
To me this is not a typical retaining wall situation that's why I am asking for help and opinions not interrogation.

I am hoping a skillful senior engineer that have encountered in his work experience in past and he is well above competition and hiding the techniques respond and help a less experienced engineer.

Thank you all ones that sincerely wanted to help and direct me.

RE: Block wall falling

To be completely honest, looking at the photo I'm inclined to think it's one of two things:

Soil movement as noted by emmgjld but you say it's on a 12" thick slab so that's unlikely.

Or

The loader operators don't know how to drive properly. The 30psf wind (stab in the dark but likely a reasonable assumption) would not cause the extent of movement shown.

RE: Block wall falling

That earlier post was how to reinforce this wall so that "bulldozers" working inside would not damage it. The many comments were sufficient to answer the question. The post was about a week ago, but I can't recall the title. other than it referred to the equipment inside and how to resist that pushing effect. My reply included several sketches of a double thick wall using the same blocks. I suspect another person did that post originally.

RE: Block wall falling

SK125POL,
Your earlier thread, as you would know, is this one:

thread507-381696: Wall for impact of Dozers

You asked for opinions, and mine is that this type wall is not suitable for the application, and needs to be replaced with a wall which is designed for the forces which will be experienced.

RE: Block wall falling

I hope you understand the harpoon suggestion was a joke and a solution not practical. What was your reaction about doubling the width of the all and making it from those same blocks? In both of your first posts you were not fully clear about what was inside and that it was not a building, but an outside enclosure. To me it looked like the typical and storage used in this country in winter. More pictures also would have helped.

By the way, most of those here review many different "rooms" and so double posting is not needed.

RE: Block wall falling

(OP)
I am seeking all possible solutions available for this case.
The owner is seeking to repair or reinforce not to re-build, this to who commented rebuild the structure.
Is there any way we could reinforce the existing wall beside laying blocks behind?
What is a proof of even laying blocks behind is adequate? Where shall I start in crunching numbers?
How do I proof that your solution on laying blocks behind with that amount will fix the problem?

RE: Block wall falling

OK here is a solution, but it likely is more expensive than doing the wall thing right to begin with. You can drive H-piling a little bit outside the wall in rows a given distance apart. Place planking in between the piles. In order to do this right you need some data. You need test borings to see what kind of ground is there to resist the loads. You need load information. The lateral "earth" pressure from the stored contents is needed. That means density and passive pressure data by angle of friction and cohesion. The "loader" ability to push is needed. Also how high up off the slab will that push be placed. I think you may have to go to a mechanical or automotive web site with the model number of that machine and ask for the maximum "push" capabilities of that machine. It can be roughed out by taking the machine weight with a full bucket and the angle of friction of the material stored there.

Use that load information to design the piling and the planking as well as finding the depth of H-pile penetration needed. You may need a geotech engineer to provide data for that design also.

Once the H piles have been driven and the planking installed, fill the opening between the old wall and the new wall with a low compressibility material, such as a low cement content concrete, or at least a well graded sand and gravel, tamped in.

If you don't care how the job looks, drive the piling next to the wall at say a 5 ft,. spacing and place blocking between the H piles (or what other pile you use) and the old wall. You still need to know all the load and soil data to do it right.

I really doubt that, leaving the old wall there, or somehow "making it internally stronger" will do the job.

Of course making sure the operator of that machine does not do any pushing of the wall also will work. That can be done by having him use his bucket to drag the excess material from the wall out into the open and doing his loading by driving parallel to the wall. For back dragging, the bucket should be in full dump position.

Just thought of another solution, but again costly. Set a quarry drill on top of the wall and drill holes all the way down through all concrete and into the earth. Spacing probably about 5 feet along the walls may be needed. Install tie-rods that are grouted into the earth below, making this a wall reinforced against bending in the planes perpendicular to the floor. If the floor is sufficiently strong you may even grout the rods to that floor, but somewhat questionable. All of these rods will best work if they are pre-loaded to provide a compression into the blocks (post stressing). You also need the horizontal loads from the stored material and the pushing machine to approximately design this system. With any fix, a design based on known loadings is the best way to be sure it will work.

RE: Block wall falling

No end to this subject I see. You need to take that machine slow moving horizontal push and allow for rapid impact. Perhaps contact the machine manufacturer and ask for an estimate of that. Probably at least double the static load, maybe triple it. From my experience with tractors and horizontal pulling, the kinetic energy of a moving machine can be significant.

RE: Block wall falling

(OP)
oldestguy (Geotechnical, thank you for your response.
I like the idea of pile and planking but try to picture it as u explained.
Would u mind kindly draw a sketch - maybe 3D showing the piles and the blocks and the planking?

Thank you

RE: Block wall falling

He described putting a shoring wall as close to the exterior face of your current wall and filling the gap between them with lean concrete or compacted sand and granular.

Is a sketch really required?

RE: Block wall falling

OK, since I have the time today, here goes. Note the piles are called H-piles due to their shape. Once you have test borings done to provide data on how deep these piles have to go, buy the material and then get a pile driving contractor, it would be my guess that the owner will opt for more of those cheap concrete blocks and rebuild the wall as I suggested in the other posting.

On the proof that the extra row of blocks will do the job, well, with the loading data and the weight of the blocks you can design the wall so that it won't tip over, because of gravity holding it there, assuming you mortar all the blocks together (making it a very heavy unit). You also may have to add dowels into the slab to create more resistance to sliding on the slab. This idea also takes into account the length of the wall, as one solid thing, not separate things. If you want to be more sure of that, add mesh steel reinforcing between each layer of blocks, designed as a horizontal beam.

With the loader on site, it would seem that all work can be done by current staff and that machine.

Let's suppose two rows of stacked blocks is not enough, of course one can add another one, but interlock all together as one unit. Seeing the current wall stood up pretty well with no special mortar or attempt to provide more over turning resisance, I'd think what I've proposed will check out fine with some rough calculations and maybe the dowels into the slab.

RE: Block wall falling

(OP)
oldestguy (Geotechnical),
Thank you very much. I greatly appreciate it.
A very elementary question - the new blocks that we are gonna stack up behind the existing wall, they don't need to be same as blocks in the existing wall (I mean same type???

The blocks in the existing wall are V-lock blocks which the key runs in the length direction and I dont know when we place them perpendicular if they just can be sat on top the key of the bottom ones???

Do you know some relaible block manufacturers?

Thank you very much

RE: Block wall falling

(OP)
oldestguy (Geotechnical),
Thank you very much. I greatly appreciate it.
A very elementary question - the new blocks that we are gonna stack up behind the existing wall, they don't need to be same as blocks in the existing wall (I mean same type???

The blocks in the existing wall are V-lock blocks which the key runs in the length direction and I dont know when we place them perpendicular if they just can be sat on top the key of the bottom ones???

Do you know some relaible block manufacturers?

Thank you very much

RE: Block wall falling

First off doing it over means starting from scratch, reusing the old blocks along with the new. You don't just add alongside the old wall. Check over those sketches provided at the other post.

Then, the original blocks must have come from some supplier locally. In the USA these are found at ready-mix concrete plants, made from the left-over concrete that was not needed at the job sites. That's why they cost less than manufactured blocks.

Next, in that one edge may have the "v" projecting out and that may be in the way of what is planned, you get the strongest guy on the job with a sledge hammer and knock that projection off. Some sawing with a hand held saw may help. For some orientations, you place the "V" notch and projections on their sides, not top and bottom, especially for the layers 2, 4, 6.

Adding the grout or concrete between layers and between adjacent blocks binds them all together. When you do this make sure the blocks are not dirty, BUT are not wetted either. The grout then will bond much better to the dry surfaced blocks.

Give this project to a person in charge who has some "know how" and can work with what is presented and understands the goal.

I may have taken the wrong slant on evaluating your comments and questions, but is there an experienced contractor in your area that can be hired with the known background experience in varied jobs? In finding such a contractor, I'd print out all these questions and answers and ask if they understand and can point to other work where they have had to do some thinking on their own to carry out a job where it had not been done before and still came out properly? It may be just one person, but with the ability to direct on-site personnel. This really is a simple job, but any job can be done wrong by the wrong person.

RE: Block wall falling

(OP)
oldestguy (Geotechnical),
Again me, I've been questioned that what is the benifit of laying blocks behind existing wall in the second layer parallel to wall?
Why not all blocks in all lawyers run same direction (which is perpendicular to wall)?
I appreciate provising a reason for this idea proposed by you.

Thank you

RE: Block wall falling

Laying blocks in layers, each 90 degrees from that below is a binding effect. You want this to result in one solid unit, especially acting like a beam on its side. Remember that shear needs some transfer resistance mechanism such that you don't necessarily want to rely only on the cementing effect of the grout. Ideally this wall will be one long unit which resists the loader pushing at any place, using the gravity and sliding resistance all along it, full length. If the wings on each end can be tied in, so much the better. That's where this "jack of all trades" supervisor comes in.

RE: Block wall falling

(OP)
So the 90 degrees from below is only useful and effective as long as we use cement/ mortar or glue the blocks to gather?

If they are loose on top of each othe the 90 degrees will not be effective, rigth?

Thank so much and also this project is in U.S.

RE: Block wall falling

The "gluing" helps greatly, but without it, there is still some resistance. However, without "glue"you won't have the full unit available for resistance against the loader.

As to the blocks, stop in a any ready mix plant and look around. Likely they have them stacked somewhat and you can see what is available. My experience with them is they are remarkably strong, even made from reject concrete at times. One project could could not have met budget if it were not for their lower cost than fancy manufactured blocks. Some landscaper material suppliers (stone, bark, etc) use them for retaining the products, but they don't have loaders doing damage.

RE: Block wall falling

(OP)
oldestguy (Geotechnical,
Thank you very much for all your kind and expert assistance.
I greatly appreciate it.

Also I really did not mean to insult anybody by posting the question in Geotech forum. I just was trying to get Geotech people opinion.

Again thank you very much.
Respectfully,
SKJ25POL (Structural)

RE: Block wall falling

Here is another option.

This alternative is assuming you are using a cement - sand grout between all members, horizontal and vertical, and you build a double thick wall, one behind the other. However, it will be necessary to tear down the present wall so that every course will have a layer of high strength geogrid laid between blocks. That grid purpose would be to tie the two walls together to create that one solid "block" of concrete. The projections and indents in the blocks will help anchor that grid also.

Do not substitute a commercial mortar mix for the cement-sand grout. They usually contain fillers and the bond strength of those mortars is way below that of a cement-sand grout.

This alternative would be easier to build and the grid tends to tighten up as the blocks are laid on it, stretching over those projections.

A stability calculation still is required to be sure it works and setting details, such as dowels in the slab.

RE: Block wall falling

(OP)
oldestguy (Geotechnical,
My boss suggesting me to use some wear steel plates against back wall (inside) attached to wall do u know by chance what is common industry practice for these plates? What type of steel? How thick? and how to attached it to the block wall?
What are possible problems?

I did not want to post a new ad but I really cant find any information off internet.

Thank you

RE: Block wall falling

In my view adding a "wear" plate inside the wall will accomplish one thong only. It will add to the cost of things and do little to nothing in the way of preventing the wall from deforming as it has. Being a structural engineer, try to show the wall would have more significant resistance to moving with the plate there. It would be a combination of structural as well as static gravity wall evaluations.

If I were in your shoes having an owner that has his own ideas on how to fix the problem, but does not want to "do it right" so it works for years to come, I'd say "good bye" and chalk up the time spent as another experience to fade into memory. Now and then we have to bite the bullet and walk away.

From my point of view, if there were other members here with different ideas that would work, you would hear about them.

RE: Block wall falling

I don't think will find an "common industry practice" because of variable situations. You are using the wrong type of wall material (mafia block) for an 8' high wall. Apparently there is a drive to use what is available and on hand to save money.

An 8' high gravity wall with heavy equipment operating in the area under little supervision could be a red flag. There is little reasonable documented information on the performance, probably because no one expected it to be used permanently.

We had 8 similar bunkers made from 12" reinforce block or reinforced concrete. There very often accessed by a big front end loader at night(24/7 operation) and never had a real problem. They were only 6' high because we wanted the "peak" of the aggregate to be less than 8' for safety and OSHA possible problems.

Just a different slant.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

RE: Block wall falling

If you don't want this block wall to fall over from the material load inside the storage area, you need to place an approximately equal amount of soil around the outside of the block wall. This will provide more than enough resistance to the blocks pushing out. The block wall would then need to be stable enough to support the outside fill when the inside is empty. The outside fill should also provide enough passive resistance to prevent the loader from pushing over the blocks. Then, to keep the loader from lifting any courses of blocks, you may need to install the steel plate armoring on the inside face of the blocks. I also think that 8' is very high for stacking a wall of 2' thick blocks, as shown in your photo. I see this all the time when driving around, but it doesn't work very well on paper.

www.PeirceEngineering.com

RE: Block wall falling

(OP)
I am sorry if my recent question was not clear.
The steel plate on inside wall is intended being added in addition to laying blocks on the outside of wall.
The peupose of the paltes are to minimize concrete chip and scraping by the loader's blade.
Dont know what's the practical size of that plate (thickness) and the type of steel plate (structural or scrap steel)?

Any body has a sample photo to show a actual one.

Thank you

RE: Block wall falling

Hey, a few more ideas. On PE's fill idea, maybe that loader guy can be kept busy adding that fill and in the process may move the blocks back where they first were placed. Only don't let him do that if the bin is empty at the time unless carefully supervised. Might push too far.

RE: Block wall falling

(OP)
oldestguy (Geotechnical),

Is it possible to mortar the 2 x 2 x 6 blocks?
What about gluing them? What are typical practical common glues? Brand name?

This is for the option of setting blocks behind wall, just to stablize them better.

Thank for any direction

RE: Block wall falling

OG back here. Mortar or grout, either have "gluing " properties. Getting the bond down between the new and the old at the vertical joint will not be perfect, but any "glue" there will help. There are epoxies that also can do the job, but expensive. Be sure all surfaces to get the mortar or grout are clean and DRY. A dry surface will absorb some of the molecules and improve the bond. If you want to improve on that, first brush on (as with a broom) a cream consistency made from Portland cement and water. The grout or mortar should be applied immediately after that. In my experience this sort of bonding is stronger than the concrete itself. Oh, don't use commercial mortar. Mix your own. Many of those mortars have fillers made from ground limestone. Masons don't like strong mortars because they are difficult to clean off finished surfaces. The easiest way to do this is with Portland cement grout and the "cream" mentioned.

RE: Block wall falling

I think that trying to mortar or glue these blocks is a waste of time and money. The wall looks like it is being pushed over. The blocks need to be backed up with some passive resistance (either soil or more blocks) and the front side needs to be protected from the loader bucket (steel plate).

www.PeirceEngineering.com

RE: Block wall falling

(OP)

The block manufacturer tells me due to weigth of blocks the mortar between will seep from joints?
Also I am not talking about between existing wall and pile of blocks, I am trying to bond the layers you draw a stecth for.

RE: Block wall falling

All I can add is cutting corners from what is likely to work, is going to result in "You get what you pay for". Also, the block guy evidently is not a mason. Try a mason for that question.

RE: Block wall falling

One final observation. The way this appears to be going, I suggest that you let the boss know that this is an unusual situation, not normally designed. As a result, perhaps he hires a consulting engineer that is well experienced in unusual situations. Getting the design from this web site probably is OK for that person wants hints as to what to do, but now it does not appear suitable under your circumstances.

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