Retaining wall - Backfill

[swisstoni]

We have had a new retaining wall built in front of an old failed garden retaining wall. The wall is 30 foot long, ranging from 4 foot high to 6 foot high.

The width of the void between the 2 walls ranges from 6 inches to 18 inches.

What is the best material to back fill with, we did contemplate concrete but the cost and the access to the wall is difficult. Thinking is 20mm gravel or MOT.

Any thoughts.

[lutonlagerlout]

is the new wall structural?
i.e. does it have rebar going into the foudation?
if so you can back fill with 10 mm shingle at the bottom then whatever
however if it is just freestanding brick work ,i would consider concrete with ties into the wall
dont forget your drainage pipes at the bottom
its the build up of water that causes retaining walls to fail
cheers LLL

[DNgroundworks]

what would be the point of backfilling with mot?

Between the two walls (the cavity) should be filled with concrete, well i always do anyway!

[DNgroundworks]

Sorry misread that

[DNgroundworks]

With LLL on the drainage, you need perforated pipe at the bottom of the void, topped of with shingle. What is the new wall built out of?

[irishpaving]

Did they place any small pipes to the lower part of the wall to allow drainage

[swisstoni]

The new wall is made of 9 inch hollow block with steel rebars filled with concrete. Its got weep holes at the bottom. There are weep holes in the old wall too.

If 10mm gravel is at the bottom what is best above, can Mot be put on top of that ?

[lutonlagerlout]

you can put anything you like really, i would suggest terram and then clean hardcore of crushed concrete,with smaller stuff as it goes up
we have just built one exactly like this ,if i remember i will take my camera in and get a piccie,the engineer said that aggregate backfill would be fine
LLL

[swisstoni]

Thanks a lot for replies on this.