russall 24th April 2008, 11:35 AM Hello,
Easy question. I am building a 1m high retaining wall using trated Pine Sleepers. I recently broke up a Patio and have about 2 cubic meters of rubble, mostly about the size of a football.
I was planning on spreading it out behind the wall then covering with soil.
Is this okay to do, I have not found any info on this for or against.
Thanks.
TommyC 24th April 2008, 11:56 AM Pros:
1. you can dispose of the concrete rubble for free
2. you will need less soil to backfill the wall
Cons:
1. the rubble is very large, and there will be lots of voids in amongst the chunks. If you top it off with soil, the soil will work its way down to fill these gaps over time, and with rain. This will result in significant subsidence at surface level.
2. you cant compact these chunks of concrete, so you cant build anything more than a garden bed on top of/behind the wall due to subsidence (see above)
Ashwood 24th April 2008, 12:06 PM Perhaps it may be possible to speed up the settlement/subsidence by using loose sand (eg. not packing sand), give it time & rain to settle, then top it with soil????
Not sure how it will work in practice, just a thought.
Ronaldo451 24th April 2008, 12:53 PM I have used concrete rubble in similar situations...as stated main issue is avoiding voids. I put in a layer of rubble (trying to avoid chunks resting on each other) covered with loose/sand soil and a bit of a hose to dampen down...another layer of rubble, sand, hose etc....
On one occassion the final layer of rubble finished at about 2/3rds the final required height so i gave it a bit of whacking with a sleeper and then covered it with some leftover scraps of blueboard to help spread any settling effect (gaps here and there for drainage) and topped up with soil. Seemed to work OK with no settling.
patty 24th April 2008, 12:58 PM Yes I have done it I excavated the front of my house down to the footings to waterproof it as we had seepage issues !! in the process I took out a set of concrete stairs big slabs and dropped them in, then filled the voids with blue metal!!!
journeyman Mick 24th April 2008, 02:22 PM Backfill with rubble and then trench rock to fill the larger voids to about 100mm from the surface. Top off with geotextile cloth and then topsoil.:2tsup:
Mick
russall 24th April 2008, 03:22 PM A lot of good advice there. Thank you all very much!
Bleedin Thumb 25th April 2008, 12:13 PM line your sleeper wall first with geotextile so dirt doesn't wash through the joins then follow Micks advise....although I wouldnt worry too much about filling the voids. I would just give it a good tamp with a plumbers bar or sledgey as I was filling it (IE in layers) to reduce the gaps.
Make sure that the rubble layer is fully enclosed in textile, and think about what is going to happen to the water that drops through the rubble IE do you need an agg drain at the bottom?
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