BOG IDEAS & INSIGHT NEEDED (PICTURES, TOO....)

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Look at the wall in the background... On the left side, the existing wall has been in place for more than 20 years. We added to it, to hold back the hill, to give them room to walk around the shed... The original block nolonger exists, but the Keystone is very similar, but what we found when we took part of the old wall apart to mate to it, there was NO rebar, no geo grid, no glue, no concrete.no extra reinforcement of any type used in the old wall... anyone can count the courses on the old wall from this picture... 7 rows of 8" tall blocks high (56") plus another 4" in height for the cap block...

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Just a close up of where the two blocks meet, and the new wall continues...

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This one just shows another section of the old wall on the right side...

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If someone doesnt like this product, that is all well and fine, we PROFESSIONALLY work with several product lines, and for a simple 2-3' tall bog, this will work with no problems... folks use the "easy to DIY" Lowe's type block with a simple back lip of concrete to secure in place, and even dry lay field and river stone without mortar to 3' heights with limited issues, and products such as the Keystone, are MUCH more secure then these other options.
 
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You are going to find them more expensive per block, than per se a Lowe's block BUT, keep in mind the dimensions are larger than most of the home center type blocks. Also, MOST of the blocks available from the home centers are NOT designed to be more than a landscape accent... the product line we like so much, the blocks weigh 80 lbs each, and are designed to BE STRUCTURAL, In our area, the retail is about $7 per block for 18"w x 8"h x 12"d... If you go to their site, check out the page specifically for this block... http://www.keystonew...ts/Compac.html# ... be sure to look through the photo gallary of some of the COMMERCIAL applications... When you see the MASSIVE retainment they are being used for, you'll understand why I am CONVINCED that something as megar as a bog is not an issue.

Also, I have been trying to organize pics (my lap top is on borrowed time), and found pics of another clients yard showing this same block again:) So here's some more pics. The wall out front was done about 10 or so years ago, and still no shifting of any kind... the backyard wall was added about 4-5 years ago...

Front...
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Out back, along the side yard...
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Close up of the steps... they are very shallow as the clients are both extremely heavy and cant do traditional height steps (brick work out front has not steps for this same reason)..
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brandonsdad02

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I had to build my bog above ground as, digging a hole wasn't a option for the space that I had to use. I used wood landscape timbers and ended up using 10 inch long Spax Power Lag screws to hold them together. They have a insanely high torqe strenght as well as there holding power. It takes a Torx 50 bit to screw them in with and you had better have a electric drill or a quality cordless drill. I used my cordless drill on the low gear and it was able to screw them in but I had to stop every 4 screws to let the drill cool down. Its started to smoke just a tiny bit so I had to. My bog isn't very big as some of the other ones on here, but it has worked great keeping the pond water clear.

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You can see how far these screws go down into the walls.
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I missed this post WB, and I have to strongly disagree with you here. We have installed two large ponds with these, as well as done walls as high as 6' tall with the same product. In one application, it is holding back a PARKING LOT, where 18' box trucks PARK parralell to the wall, and only away from the blocks by a max of 3'... will look through my computer to see if I can find the pictures. If not, I can shoot over and grab new pics of the wall holding back the parking lot, as that is only down the street from me. That wall has been in place for 8-10 years now, without a single issue of any type.
You aren't really disagreeing with me, you're disagreeing with the manufacturer. What I posted was based on specs published by Keystone. They do pretty extensive testing imo, way more than I could ever hope to do. I know lots of people don't believe anything less they see it for themselves, but I'm not one. There is just no way I would have the time or $$$ to test every product for myself. And I don't see the need. I rely on reputable companies testing to industry developed standards for most of my info. Doesn't mean the info is perfect, just the best I think I can obtain. I trust the current system to a very large degree.

The parking lot wall I assume used a block and system specifically engineered for that application. Here's a Keystone wall that looks to be about 30' tall. Those are not the same blocks you get at the Home Depot. And I assume they also used something like their KeyStrip steel reinforcement mesh which goes back into the earth several feet which isn't possible in a pond application. I also assume the soil was engineered or certainly at lease tested to make sure it was within spec.
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As I said in earlier posts...this isn't digital. If you build a pond wall out of any material or system there is never going to be a way to say that 2' high will never have a problem, but 2' 1" will fail immediately. Specs are about risk and expectations. When they say a the max height for block X installed to spec is 3' for soil they mean they have a high expectation it will remain unchanged for a very long time. That in no way means a 4' wall won't perform the same for many, many applications, but the manufacturer's expectations are that some cases will fail. There's no way to predict who will be the lucky ones.

Keystone doesn't have any specs for holding back water because their products aren't designed for that application. They're designed to hold back soil (lateral earth pressure). Water, or even certain saturated soils, is much higher (hydrostatic pressure). Here's a good forum if you really want to get into the details. They are very nice and helpful answering questions.

That you used something and yours didn't fail doesn't disprove the manufacturer's claims to me. I'm happy for you and glad you've been lucky. You are certainly free to build in any manner you wish. I do think you're confusing luck with specification. There are thousands of posts in all kinds of forums that are similar. "I've smoked for 40 years and I've never had a problem" type logic to me just isn't that convincing. I know many people consider it better than science, just not me.

I don't always follow specification but I also know I'm taking risk. For example I might build a 3' high pond in my backyard with Keystone block, if the failure wouldn't be a big deal. If I was keeping $25,000 worth of Koi in that pond...I don't think I'd take the risk. A 6' high pond wall? Failure could kill someone and there's no way I would ever take that risk. That's a good way to win a Darwin Award. It has been my personal goal in life to not get a Darwin. I've been close a few times though.
 

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NOW, not to derail the wonderful, informative dialogs regarding retaining walls -- I have another question about "bogs," but think I'll post it in my current "trickle tower/shower" thread as it sort of applies both places. It has to do with the bioconversion issue.
 

Mmathis

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Keystone doesn't have any specs for holding back water because their products aren't designed for that application. They're designed to hold back soil (lateral earth pressure). Water, or even certain saturated soils, is much higher (hydrostatic pressure). Here's a good forum if you really want to get into the details. They are very nice and helpful answering questions.

WB, that information was way too technical for me, but reading through it [I think] helped a little. At least, even if I didn't understand what I was reading, my puny little brain did start to ask some questions regarding retaining walls. This is my basic understanding of what I'm up against, and you guys can correct and/or fill in the blanks.

My first thoughts were that the retaining wall would collapse outward, or just sink and fall down over time.

But a wall has to exert pressure back in the direction of the load to keep it from falling over. If the "load" is just dirt, and all it does is sit there, the pressures can equal each other out and the wall stands. But with a pond [or bog in this case] there is basically a big hole on the other side of the wall. I'll have a liner in mine and it will contain gravel and water. But won't there be an inside-the-wall pressure or force tugging at the walls via the liner, wanting to pull them toward the center? When I visualize a hole with a wall around it, I see "wall" being pulled inward. So that's where the rebar & cement come into play, stabilizing this wall?

So what exactly DOES happen when a wall like this fails? What are the forces that cause it to fail? And how do certain practices keep it from happening?
 

brandonsdad02

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The block wall with a liner stacked up 2-3' high should work fine. If you put your liner up to the top and then put a cap on it the, the weight of the water would want to pull it in. But since you are filling with gravel, the gravel will push back on the wall keeping the forces on each side the same.
 
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My first thoughts were that the retaining wall would collapse outward, or just sink and fall down over time.
Yes, the pressure is outward. The end result is the wall moves outward. The actual pressures are more complex. For example pressure increases the deeper you go so the wall is being pushed out at the bottom, which can cause the top of the wall to move inward. But as the failure proceeds the structure of wall changes quickly as it breaks apart and pressures also change fast.

But a wall has to exert pressure back in the direction of the load to keep it from falling over.
A vertical wall doesn't exert any pressure backward. It's purely a strength thing, tensile and shear. For example the stacked blocks depend on friction of the blocks sliding (shear) and anything else like pins, adhesive, concrete lip on the block (tensile and shear). A hollow block filled with concrete has way higher tensile and shear strength than stacked block. Poured concrete with rebar has even more.

If the "load" is just dirt, and all it does is sit there, the pressures can equal each other out and the wall stands.
Yes. The pressure on both sides of the wall would just be air pressure. A brand new soil retaining wall generally holds back very little pressure. It's only later when soil is saturated or during earthquakes (soil liquefaction) that the soil starts to really push against a wall.

But with a pond [or bog in this case] there is basically a big hole on the other side of the wall.
My earlier posts were only about the portion of a wall that was above ground. A hole with a liner generally needs no wall of any kind. This more true with soil sides that slope out, vertical are more prone to collapse. Even less likely for bogs because gravel locks together to some degree and doesn't want to move out of the way like water is happy to do.

I'll have a liner in mine and it will contain gravel and water. But won't there be an inside-the-wall pressure or force tugging at the walls via the liner, wanting to pull them toward the center? When I visualize a hole with a wall around it, I see "wall" being pulled inward.
Not really, if I'm following you. Water pushes the liner against the soil. It would take a lot of pulling to overcome that friction. Liner would rip before overcoming that friction I think. Liner is "glued" to the soil.

So that's where the rebar & cement come into play, stabilizing this wall?
It resists both inward and outward pressure.

So what exactly DOES happen when a wall like this fails? What are the forces that cause it to fail? And how do certain practices keep it from happening?
It depends on the application and material. To answer the question fully requires 4 years at university. To answer it simply would be kind of lame, which is the only way I could because I only have a slight understanding of the basics. I think it's easier to look at other failures because the same issues come up over and over.

That's why I rely on documented standard building practices. Someone else (actually thousands of people) have already done the work for me and if they say a 3' high (above ground) wall must be built 1,2,3, I build it 1,2,3. Uncle Ernie will tell me "Oh you can skip step 2. I did and never had a problem". I just get Uncle Ernie another beer and "waste my time" and do step 2 anyways. I have no idea if Uncle Ernie is right or not. How could I? I mean I could listen to my gut, but that's pretty lame. My gut sure isn't a Structural Engineer. For sure I know Uncle Ernie doesn't know if he's right or not, he just thinks he's right. There's a difference.

Or I might be Uncle Ernie and skip step 2. But I don't kid myself in to thinking I know better than the thousands of engineers who figured this all out for me. I cut corners to save time/$$$, but I'm clear I am cutting a corner. I think where people get into trouble is thinking they just intuitively know stuff and cutting one corner leads to cutting another, and another until you really do have a problem.

Here's an example from another forum. Not important who, WE ALL cut corners before we learn better.
CornerFailure.jpg


In this case 3 standard practices were skipped. No rebar. Adjacent vertical joints not staggered. Cores not filled with concrete. If I remember right rebar was used in other parts but corners require the blocks to be cut so horizontal rebar can pass thru. Skipping that step, lead to not being able to use rebar, which lead to failure. Sneaks up on you. And the builder didn't realize how weak corners are to start with.

BTW, this picture also shows, at least to me, the problem with stacked landscape block for an above ground pond/bog. The biggest weakness is the corners. Soil retaining walls don't have corners. This can be reduced by making the structure a circle, but the basic weakness is stiil there. Landscape blocks have nothing in the vertical joint to hold blocks together. Even the wall in the picture had a little mortar. Landscape block would only have it's mass which isn't much compared to the water mass.

The pond in the picture was fixed by wrapping the walls in steel. The same could be done with landscape block, but pretty expensive imo.
 
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Your example of the cinder blocks IS a great example of what NOT to do. It is clear from this photo that it is NOT structural sound by any means and failure was a matter of time.
 
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I guess my retaining wall is going to fail then. Mine has a corner where is goes around the old cement steps that were going up the hill from the walk out basement.

The whole issue Ryan comes down to what a wall is built with, and specifically, in what method... I cant comment on your retaining wall, as no info was provided. The issue I have with WB's comments is he is IMO over analyzing. He appears to be reading specs, with limited hands on experience, or at least with the product/method I am personally defending. Not everything he is saying is without a valid reason for a concern. I have witnessed these products in place up to 20 years, with no issues to date... I think that is a pretty good track record, even if the manufacturer doesnt include the details of ALL applications in their specs.
 

brandonsdad02

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Here is my wall. I have no clue what kind the blocks are. We got 400 of these blocks off of craigslist. They are 18 inches long, 10.5 deep and 4.25 tall. They are solid cement with 2 holes in them that I guess you could run rebar down thru the holes. They are super heavy. From the picture you can see at the base of the wall a different colored patio stones. We extended the patio by 2 feet then we built the wall. There is no mesh or anything in the layers of the wall stones. Just the stones off set stacked.
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Here you can see my corner that will fail I guess. No rebar was used in the whole wall, just the wall stones.

Cape, thats my problem that I have with a lot of WB's post. Just over thinks way too much. Don't get me wrong, there is nothing wrong with over thinking things, because I tend to do it myself about things, but when it comes to alot of the stuff on here. I just need regular terms. If I need a 9 yr degree from harvard to understand how to build a retaining wall that will with stand the zombie take over and the next ice age, then that is over thinking the problem at hand. I guess for me being a new construction electrician for 6 years and being on job sites and seeing first hand how things are built from the structural stand point, its just kinda second nature to me.
 

brandonsdad02

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I also don't see a pond pictured in WB's post about the block wall that had cracked. It looked to me that they joints were staggered, If you look at the bottom block, it was cracked in half. That isn't easy to do with those types of blocks. Almost looks as if that was a result or a earthquake or something similar. Not really enough info of the pictures to see what really went on.
 

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