Block wall falling

[SKJ25POL]

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?

 

[jayrod12]

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?

 

[concretemasonry]

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.

 

[emmgjld]

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?

 

[oldestguy]

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.

 

[SKJ25POL]

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.

 

[jayrod12]

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.

 

[oldestguy]

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.

 

[oldestguy]

Looks to me you forgot the post under "Other Structural eng'r". Seems to be your name there?

http://www.eng-tips.com/viewthread.cfm?qid=381696

Referring to "bulldozers" when you probably meant "loaders".

 

[hokie66]

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

thread507-381696

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.

 

[oldestguy]

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.

 

[SKJ25POL]

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?

 

[oldestguy]

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.

 

[oldestguy]

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.

 

[SKJ25POL]

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

 

[jayrod12]

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?

 

[oldestguy]

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.

 

[SKJ25POL]

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

 

[SKJ25POL]

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

 

[oldestguy]

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.