LinkBack URL
About LinkBacks
Reply With QuoteI'll let the experts give real advice but thinking that you may have to go down some more until you hit solid stuff.Perhaps you could find a couple of old 200 litre drums and cut the top and bottoms out and use those as caissons?
Fence post hole wet and walls collapsing in faster than I can dig it out Fence post hole walls wet and collapsing in faster than I can dig
I dug a hole for a fence post 800mm deep about a week ago. I ran out of time to set the post that day so left it overnight. Next morning the hole was about 1/3 full of water. I could see it seeping in through the walls. Wasn’t sure what to do so just refilled the hole with the intent to come back later and re-dig it and put in the post.
Fast forward 9 days and I’ve just attempted to re-dig the hole but it is so wet the walls keep collapsing in faster than I can dig it out. Admittedly it has rained a LOT the last 48 hrs so maybe I’m just an idiot for trying to dig it again so soon without letting it dry out? Or have I made a big mistake refilling the hole 9 days ago?
Should I wait for a nice dry spell to let the soil dry out? The hole is 800mm deep and the walls from about 500mm down are collapsing (the upper part of the hole holds its shape) so not sure dry weather is really going to affect that deep in the ground? Is there any way to get the walls to hold for an hour while I set the post and pour the concrete (eg refill with some sand mixed in or something)?
Total novice here and did not note down “wet post hole” on my things that could go wrong napkin.
Thanks
I'll let the experts give real advice but thinking that you may have to go down some more until you hit solid stuff.Perhaps you could find a couple of old 200 litre drums and cut the top and bottoms out and use those as caissons?
"A big boy did it and ran away"
Legal disclaimer denying responsibility to be inserted here.
The ground is waterlogged, best approach is back fill and wait until it dries out. Try again after a couple of weeks of dry weather. The alternative is to line the hole however I doubt that is possible.
I suspect as you dig water flow from the surrounding ground is collapsing the walls. Refilling with soil reduces the scale to a hole rather than a crater
The solid stuff is at 800mm. I’m so close but the collapsing walls keeps covering it over too fast. I had a similar thought about a caisson of some kind but not sure how to do that.Originally Posted by Moondog55
Waterlogged sounds right. I could see tiny trickles of water flowing into the hole as I was digging. I was worried about how much to keep trying considering, as you say, it could become a crater a totally collapse.
We have a lot of wet weather forecast (la nina summer for us here on the east coast of oz) so I might be waiting a while!
Is there something about refilling a hole in this situation which means that the ground is never quite the same? The ground had been settled for a long time before I dug it up. But now it’s been refilled does it need time to resettle or get compacted back down?
It never fully resettles, the damage is done but it is after all only a post hole so not a big deal. When dry remove the loose fill you tossed back in, then take a shaving all round most likely you will have quite a stable wall in the post hole. Don't overthink it, if the ground gets that wet you will never have a rock solid post during wet periods but will be stable when dry.
Thought I’d post an update on this. So it turns out after some investigation that my mains water pipe, which is situated about a meter from my hole, was leaking. It was a small leak about 400mm below ground level. Long story short - got this fixed and then waited a week and had another go at digging the post hole. No issues this time! Managed to dig the hole all the way down without any evidence of water seeping in and the walls held up. There were a few areas where I could see the wall was coming away a bit from when I last dig it out but otherwise it was fine. Post is now in and solid.
Anyway, not particularly helpful for someone with a genuinely waterlogged hole, but something to check for in case you are near a mains pipe. I also did not need to use my home-made caisson…little but bummed about that.
Posting Permissions