Concrete block retaining wall repair

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Old 05-17-05, 05:33 PM
jlh
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Question Concrete block retaining wall repair

Part of a retaining wall that was installed before adequate settling of the underlying soil occured is now in need of repair The wall is made of 80 lb concrete blocks and block adhesive was used during the original construction (3 years old). I want to know how to best dismantle the part I need to repair without destroying the blocks - if that is possible. I have tried prying the cap blocks off with a pry bar but am hesitant to apply to much force for fear it is just going to damage the blocks. I want to find someone who has done this before I start wailing on the thing assuming the only way ahead is to destroy and rebuild with new material Thanks!
 
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Old 05-17-05, 09:31 PM
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Concrete block retaining wall repair

Its a good thing you don't have a rigid wall with a rigid footing that will ultimately crack and possibly be all waste to haul away.

Segmental retaining walls (SRWs) can be rebuilt when you have a major settlement of of the lower soils.

I assume you are correct in saying the problem is because of a vertical failure of the lower soil and not excessive horizontal load on the wall from the backfill.

The cap blocks are usually adhered to the main retaining wall block with a flexible sealer (silicon possibly). This has no structural purpose and its only purpose is to prevent the caps from sliding off. Usually there are a few dabs. You may be able to insert a thin blade into the horizontal joints and cut the caps free. If not, you may have to sacrifice a few cap units to get an opening so you can pry off the remaining caps.

The main blocks in a properly built SRW wall are not adhered together. They have a means to prevent the units from sliding relative to each other. The two ways of preventing the sliding are with a concrete lip cast in the block units or by using vertical fiberglass or fiber reinforced plastic pins inserted into the block and another block set on top. In either case, you should be able to dissassemble the block and stock them for rebuilding later. If your wall is built using pins, be sure you save them since it may be difficult to easily find additional pins of the same dimeter and material.

If this is a major wall, have a soils engineer take a look and possibly put in a couple of shallow (10') holes to see what you have and how to correct it.

If it is not a major wall, excavate a foot ot two feet of the base and possibly widen the base out a bit toward the front to spread out the loads. You don't want to remove everything below to this will let you live with it. Put in good base material and compact it well. If the old wall had any drain pipe reinstall them. If not, put some in and use a granular backfill. This is cheap insurance and will reduce the weight of the wall and soil on top of the poor soil (wet soil weighs a lot more than dry).

Do not ever let anyone talk you into putting a rigid reinforced concrete footing under a SRW wall. This destroys the advantage of the wall system that is the ability to move very slightly at each block. Rigid structure will break into 2 or 3 huge chunks of waste that cannot be repaired.

If the SRWs are one of the nationally licensed systems, the licensing company may be able to give you additional assistance on how to rebuild. All of the the major systems have web sites. Anchor Wall Systems, Allan Block, Keystone and Versalok are the main licensors with good engineering staffs. They may be interested if you document the progress.

Good luck!!

Dick
 
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