Segmented Block Options

LNG24

Has anyone ever stacked a segmented block wall with motor joints? In other words, use the block in a traditional cinder block construction technique. Reason: No room for the GEO fabric to do a hold back, but we can motor the joints and fill it with concrete along with rebar

Why this block? I can get it really cheep, like free

CJKarl

If no room for geotec then are you actually holding back a lot of soil?

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AtlRemodeling

LNG,

There are a lot of questions that need answer before anyone could approve this type of structure.

1) How high is the wall?
2) Are there slopes above or below the wall?
3) Are there any loads above the wall?
4) How much room do you have behind the wall for excavation?
5) What type of block are you using?

The modular blocks are designed not to be mortared so that hydrostatic pressure does not build up behind the wall. However, many of the block manufacturers does have provisions for filling the cells with concrete/rebar re-enforcement.

Most modular blocks can go about 42" simply as a gravity wall (no geogrid). But there are also many "tricks of the trade" to allow taller structures without geogrid re-enforcement.

I spent 8 years as one of the largest installers of Allan block in Georgia but I was a certified in nearly every block made. Let us know what your facing and I should be able to help out.

concretemasonry

When you start using mortar, you are building a different type of wall (rigid) that also needs a footing below frost. - This is the old style that has a lot of problems.

If you use semental retaining wall block (SRWs), you have to go by the design and construction methods recommended for the different types. These walls do not need footings and can go 40' high, but will generally require geogris for over about 4' depending on the soil.

In your situation it appears you are over the 3 or 4' limit.

You need someone to design the wall to protect yourself, whether is is an SRW wall or a conventional retaining wall with mortar, steel, grout and a footing.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

LNG24

Wall is only going 4' high to grade
No slope.
We are putting in a footing & drainage behind wall.
Design was approved for 8" Concrete Block filled solid plus Rebar sitting on footing.

Only difference as far as I can see is that instead of using 8" block we are using 12" SRW block.

I know the disadvantages of bolck over poured and I have even seen a number of SR Walls failing too, but my queston is: Do you know of a major difference between the two blocks?

Tscarborough

The main difference is the price. Why would you pay 6-7 bucks for an SRW when a normal split-Face block is 3-4?

And that is leaving aside the issues of changing an engineered design on the jobsite.

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concretemasonry

How do you propose to build a vertical wall with SRWs? Usually they have a shear projection on either the top or bottom to give a batter to the walls. - The exception would be a pinned system or a cheap "knock-off" block that is similar to a regular shape block. Some producers in your area may make the "knock-offfs" because they cannot get a license to produce the units/product lines that are approved by municipalites.

Without knowing what kind of block you have, it is difficult to say how it would work and if the cores would line up for the rebars. If the block are made to fit to a curve, the mortared head joints would be very difficult to do. - especially on the back side. Since you are doing a rigid wall, you probably have to use a bond beam with horizontal steel in it as a top structural course and this could be a problem with a SRW unit that does not need any horizontal steel to keep the block together.

It is difficult to believe that you would need geogrid for a 4' high wall with a good SRW unit. You may want to look into making your job easier and cheaper by using the almost "Free" block the way they are designed to be used. All of the major types have great web sites complete with design and construction details. Look for the sites for Allan Block, Anchor Wall Systems, Keystone and Versalok since all are made in your area and you may have one of those types.

SRWs only fail when they are not installed correctly. Rigid walls usually fail because the are not built or designed correctly. Around here, counties and mucipalities will not use poured or reinforced walls and almost exclusively use SRWs for that height because they are flexible, do not require excesive excavation to get deep enough and can be shaped to fit the grade and curvature since they are designed specifically for retaining walls and not just adapted.

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

AtlRemodeling

With a 4' wall and no slopes or loads you should be fine as long as you've got good drainage and good draining soil. Here in Georgia all we have is clay which gets extremely heavy and will push walls around.

Worse case scenario you would need 3 feet of grid (measured from the front face of the wall) according to my design software. You will already have to excavate 2' (1' for the depth of the block and 1' for the gravel); can you dig out another foot? If you can I would put the grid in. The cost is minimal compared to repairing the wall if it fails.