Posthole Digger Fence posts in sand??

[hunt4570]

OK, not sure if this is the right place for this, but I'll be using a 3ph auger on my Kubota to drill the holes, and thats an attachment right?..

Ok, putting up a fence here at my new place in South Carolina, I'm new to South Carolina and to the new soil under my feet. The power company was here the other day to run underground cable to juice up my new barn and I noticed while they were digging that the ground was pure sand! They dug a trench about 10" wide and 3 feet deep.. looked like they were digging in a moist sand dune.

Now I'm looking to put up some fencing, I've always dug the hole, put the post in, then returned the soil to the hole a little at a time while packing it down firmly with a large steel tool made for the job. I've never dealt with sand like this before and was wondering if I can still do this. Will the sand compact enough to hold the posts tight? Do I need to throw quickcrete in the holes?

Anyone out there with experience setting posts in sand that can help me with this question?

Again, not sure if this is the place to put this, sorry if its in the wrong place.

 

[txdon]

You might have to add water when you are digging to keep the sand from falling back in the hole if the sand is like sugar. Water may also be needed to get the sand to pack well when you tamp the holes shut. I did not use cement in my sugar sand and the fence has been up for 20 years with no problems.

 

[hunt4570]

Quite a bit of moisture in the sand already.. when they dug the trench the walls stayed put fine..

so your posts stayed tight in the sand ok then...

 

[CDN Farm Boy]

If you run into the sides collapsing on you, you can try a piece of pipe just larger than the auger as a sleeve for the hole. Rig it up that it goes down with the auger by having a plate on the drive head to push on the pipe with a couple large holes near the top for the sand to escape. Once you reach your desired depth, pull out the auger leaving the pipe in place. Drop in your post, backfill just enough to hold the bottom from moving then pull the pipe out with a chain and then backfill the rest of the hole.

I saw a fence contractor doing this once years ago and thought it was brilliant and filed the idea away for future. Mind you, they were using a fullsize Cat backhoe so not sure how well it would work on a CUT.

 

[EddieWalker]

Sand is the weakest of all the soil types out there. You will need more H post closer together compared to a fence in clay or another type of dirt. I would also go deeper. Your 3pt auger is only going to go down three feet. I would feel a lot more comfortable with a 4 foot hole. You can buy an extension that you add to your auger once it's down in the hole that will give you another foot. It's a pain to do this over and over again, but it's easier then dealing with posts that move after the fence is done.

You really cant compact sand like you do dirt. Just put the sand back in the hole and dump a massive amount of water in there. I would start with a five gallon bucket and see what happens. The water will compact the sand. On big construction jobs I used to run the water truck and I had an attachment on the end of the hose that I would put into the sand and shoot water into it as deep as I could get. It was called jetting the sand. The water would saturate the sand and it would collapse onto itself. This is as good and solid as you can get sand once the water drains away.

Eddie

 

[LiveRoll]

Or instead of augering in the posts perhaps renting a post pounder, and just driving them in to 4 feet or so. kind of redundant with you already having an auger, but it may be a lot less trouble and labour involvement.


Cheers

Roger

 

[countrybumpkin]

Sand is the weakest of all the soil types out there. You will need more H post closer together compared to a fence in clay or another type of dirt. I would also go deeper. Your 3pt auger is only going to go down three feet. I would feel a lot more comfortable with a 4 foot hole. You can buy an extension that you add to your auger once it's down in the hole that will give you another foot. It's a pain to do this over and over again, but it's easier then dealing with posts that move after the fence is done. You really cant compact sand like you do dirt. Just put the sand back in the hole and dump a massive amount of water in there. I would start with a five gallon bucket and see what happens. The water will compact the sand. On big construction jobs I used to run the water truck and I had an attachment on the end of the hose that I would put into the sand and shoot water into it as deep as I could get. It was called jetting the sand. The water would saturate the sand and it would collapse onto itself. This is as good and solid as you can get sand once the water drains away. Eddie

This!

 

[davesl708]

I was just wondering if you mixed a little Portland cement into the sand before you put it back in the hole would help the compaction.
I have seen this used in rammed earth home construction when using topsoil. They mixed it into the topsoil with a rototiller then compacted it. Does not require much. Maybe one cup per hole.
Colloids in the Portland helped bind the soil.

 

[Billrog]

30" deep with 1 shovel full of concrete at the bottom and 1 more 6" from the top of the hole or just pound them in.

 

[almaryholm]

Mix crushed stone or smaller rocks with sand as you backfill/ tamp around posts.... ( filling only a few inches at a time )