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Working around retaining wall obstruction
I need to build a series of stepped retaining walls. One of the walls needs to be built right where four plastic Sched. 40 pvc electrical conduits are run. The conduit crosses the path of the wall at an oblique angle, maybe 15 degrees. Each wall will be 4 feet or less in height and the conduit would pass through the wall in the second or third layer of vertical blocks.
Is there a reasonable way to resolve this without pulling the wires and running new conduit?
Maybe a few blocks could be cut to allow the conduit to pass through and the voids filled with compacted sand?
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Working around retaining wall obstruction
Mayber split some Sched 80 the next size biggeer then clamp it around the erxisting conduit woth stainless hose clamps??? Just a thought. Frank.
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Working around retaining wall obstruction
Ken, we run into this quite a bit.
The two favourite methods of dealing with it are to either move the conduit or wall slightly so as to prevent the two from ever meeting. This is best since eventually one will need to be worked on and the other will create a PITA. The other method is to cut (VERY gently) through the conduit and install a couple of 90° elbows and a short piece of straight pipe so the conduit goes through the wall at as close to 90° as possible.
Don't forget, the bigger and especially longer the hole is, the less connection there is between the layers in that location. That will cause a weak spot that might cause if not accelerate the failure of the wall in that location.
If they must cross each others path at a shallow angle like that, try to make one go over the other instead of through. Often you can dig up enough of the conduit in each direction to lower it enough to clear the wall.
If at all possible, when a conduit crosses under a wall, protect the conduit with a 'bridge' consisting of sand around the conduit, and especially above, then a solid layer, concrete or preserved wood, then gravel. This will spread the load out and prevent the wall from settling and breaking open the conduit.
Best of luck.
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Working around retaining wall obstruction
Thanks, Murf, that's what I feared. What if we were to build
a small concrete form in place of one of the blocks and pour
some concrete around it? This would be in a layer of block
that would be buried so appearance isn't an issue.
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Working around retaining wall obstruction
KW are you using geogrid between the lifts of backfill?
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Working around retaining wall obstruction
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KW are you using geogrid between the lifts of backfill?
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No plans for geogrid. I'm planning on a base of compacted sand with drainage (gravel,drain pipe,fabric) at the rear base of the wall.
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Working around retaining wall obstruction
KW have you heard of the enemy to construction projects? His name is Gravity.
If I understand your description of the job, you might want to consider using the geogrid to keep the walls from bulging over time. And compacted sand is fine providing there is resistance i.e. walls to keep it in place. As soon as the reatineing system moves it's no longer compacted. And it depends on the type of sand you're using too--some sand does not ever compact; others can compact beyond belief. We call the latter around here "sharp sand" which has jagged sharp edges that interlock. For road building and backfilling basement digs, we use a Class 2 sand.
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Working around retaining wall obstruction
According to the block manufacturer geogrid is not necessary for walls less than 4 feet high. Have you found that not to be true?
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Working around retaining wall obstruction
Here's a case in point: A local developer--who should have known better-- built a big home in the middle of wet lands on a mound of dirt that was just big enough to place the home. The driveway was about 20 feet wide and 150 long and made a lazy curve toward the home on each side. Both sides were formed of 90 lb. retaining blocks 4 feet high. The 20' x 4' x 150' drive was filled with crushed stone. No geogrid was used. Then an 80,000lb. concrete truck drove about 5-6 feet from the edge and took out about 75 feet of wall on one side.
The builder had me dig out half the width of the driveway down 4 feet and rebuild the wall this time with geogrid every other course.
After it was all done, later another cement truck was able to drive right next to the block wall and didn't even move the blocks, according to the builder who was ecstatic it worked.
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Working around retaining wall obstruction
Thanks for the info. There's no way a cement truck could drive in this area but the upper wall will be about the minimum allowable distance from a shed and a tractor may be driven parallel above the lower wall. I'll see about putting in some geogrid too.
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