A hole

[i_am_fubar]

I've been digging the foundation trench for my retaining wall, and I seem to have come across a large pocket of loose agrigate. My soil is heavy clay.

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• i_am_fubar
• 5 Apr 2010
• 1

I first noticed it knockling the marking stakes in (shown in red). One just didn't stop going in, and easily pulled out. On further digging, I started lifting out this agrigate. It extends some way under the patio to the side. but I've no idea how much.

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• i_am_fubar
• 5 Apr 2010
• 1

What could this be? Builders waste? a soakaway (under where we used to have ponds)? There were a couple of concrete blocks dumped over the top.

And more importantly, what should I do about it? I could dig down a few inches and cover up with clay and lay ontop of it. or douse it with cement and let it harden. Or, do I have to remove it all to make a stable base?

 

[i_am_fubar]

Have been thinking about this. There is a drain access cover not far from this gravel. Never seen water in it.

Could the gravel be a soak away from the garage area behind my house where the access covered pipe is an overflow into the sewer?

 

[freddiemercurystwin]

Just to get the ball rolling as no one else has, if all it is is gravel I'd remove it and refill the void with MOT1 compacted in layers. Often when bad advice is given (like this may well be ) the regulars in the know will correctly advise, hopefully! Or they'll confirm it as good advice.

 

[Thermo]

how big is the retaining wall?

 

[i_am_fubar]

See my post about the retaining wall construction here:

//www.diynot.com/forums/viewtopic.php?t=215729

These dims, but without the rear buttress.

Digging it all out is not an idea I'm particularly keen on as I have no idea how much is in there. I've filled a trug up already, and it shows no sign of being empty.

 

[Static]

Check where your roof drainage points.. as others have said sounds alot like a soakaway..

If its not a huge soft spot (so less than a metre or so) then you can probably bridge it with some reinforcement in the bottom of the footing.. just make sure the ground each side is pretty solid..

 

[i_am_fubar]

I'm going to be laying 2 lengths of rebar in the foundations throughout the entire footing. My house drainage is nowhere near it, however there is a garage block backing onto it that it could be.

Could I use this soak away (if it is indeed one) for drainage of the retaining wall?

I will also stick a smoke bomb in the drain cover a short distance from it and see if anything comes through.

 

[Static]

Could I use this soak away (if it is indeed one) for drainage of the retaining wall?

Not really.. unless you are gonna move the retaining wall away from the soakaway..

Just make sure you put rebar in the hollow cores as someone suggests in your thread, and definitely no horizontal DPC..

 

[i_am_fubar]

Can't afford to move it. The location is based on existing patio area and location of garage wall.

Rebar in the voids will not be a problem.

Will drain into the drain then.

Any new ideas on how to deal with this gravel? I would really like to not remove it.

 

[Static]

Rebar in the voids will not be a problem.

Retaining walls work on dead weight of the wall itself so fill the cores with concrete too.. heavy wall = longer wall life

Will drain into the drain then.

Weepholes and the little trickle of water youll get every now and then can seep through.. draining your whole garden into a surface water drain isnt a great idea.. your trees should soak up most of the moisture..

Any new ideas on how to deal with this gravel? I would really like to not remove it.

Pretty sure i said put some rebar in the bottom of the footing over the soft spot to bridge it.. 3-4 x 10mm bars in the bottom, extending 1m beyond the patch each side should be plenty..

 

[i_am_fubar]

More steal and concrete. That I can do... No duck tape though?

Anyway, cheers for that, I'll reinforce the corner and stick weep holes in. I assume I'll still need the waterproof membrane at the back.

Also, the trees are now gone with the exception of the fig.

 

[Static]

DPM (either a sheet or black jack painted on the rear) is a better way to go, without one water will leach through the wall and cause stains to appear (normally brown ones).. and a weep holes about every 1.5m or so..