Little help figuring out how to "bell" my piers.

[Duffster]

When I put a post in I put the post, concrete and all of the dirt back in the hole. Nothing is spongy or holding water.

 

[PILOON]

One easy way to create the bell at bottom of the tube is to slit the tube about a foot on 5 or six sides. When you fill the tube the weight of the crete will splay that foot outwards and create your bell.
Not as pretty, but gets the job done and the extra crete is less than the cost of of the plastic feet.
Still another method is to pour some crete to fill the bottom of the hole before you sit the tube in it. The whole purpose of the bell is to create a bigger footprint for loads and resistnce to frost upheaves.
I have seen blob bases poured, tube inserted with gradual backfilling done to stabilize the tube in the vertical position.
In all cases some crushed stone should be the first material placed in the bottom of the post hole.

 

[EddieWalker]

When I put a post in I put the post, concrete and all of the dirt back in the hole. Nothing is spongy or holding water.

Any disturbed soil will hold more water then undisturbed soil. It's not that it becomes "spongy" but that it holds more water and has a higher water content then undisturbed soil.

If you've done any underground utility work, and had to dig trenches for multiple lines, like water and power, Code in the areas that I've worked, CA and TX, require virgin, undesturbed soil between the trenches. The distance seems to vary depending on who is in charge, but what is important is that there is a wall of virgin soil between the trenches.

No matter how hard you compact the soil, you will never get it back to 100 percent like it was before you dug it. Code where I've worked was in the upper 90 percent and it was tested with a radiactive sort of sonar device that sent a signal into the dirt that bounced back to tell us if we passed compaction or not. At 98 %, which is just about perfect, it still wasn't as solid as undisturbed soil.

Are you saying that your backfilling around a post is going to be better then that?

Using the back of the shovel, and other hand held tools to compact around a post if good enough for a pole barn or fence post. If there is a crown at the top of the post, it will help shed water, but that soil is also going to get more water in it then the soil that was never dug.

Eddie

 

[Duffster]

No matter how hard you compact the soil, you will never get it back to 100 percent like it was before you dug it.

If you put the post, concrete and ALL of the dirt back in the hole it is compacted harder then it was origianlly now isn't it?

 

[EddieWalker]

If you put the post, concrete and ALL of the dirt back in the hole it is compacted harder then it was origianlly now isn't it?

I'm confused on the putting the dirt back into the hole part. If you fill the hole with concrete, then yes, I'm in total agreement with you. I just don't understand what you mean by putting the dirt back in the hole?

Eddie

 

[Bartcephus]

The bell is to spread the load without requiring a column the same diameter all the way to the surface. It is a concrete saving solution opposed to requiring 36 inch column of concrete all the way up. As far as "more resistance to upheaving" I would suspect that is guaged more by the depth of the pier than that of the "bell" on the column. Getting sufficeintly below the frost depth is the key to reducing the risk of heaving. The spreading of the load gives more weight bearing capacity to the pier in compression.

 

[Duffster]

I'm confused on the putting the dirt back into the hole part. If you fill the hole with concrete, then yes, I'm in total agreement with you. I just don't understand what you mean by putting the dirt back in the hole?

Eddie

I only put concrete in the bottom of the hole.

This gives more resistance to uplift then filling the entire hole with concrete.

 

[tommu56]

My piers are square dug with my hoe approximately 36" square with a grid of rebar in the bottom and a couple of L shaped pieces in the center pointing up. I wire all the rebar together and space it off the bottom with some concrete or brick scraps,
I make the first pour about 12" thick then stick the sonatube over the vertical bars push it in to the wet concrete anchor it, plumb and back fill it carefully right over the wet concrete.
Then shoot the level and mark and cut off the tube at the correct elevation and then pour it.

 

[Keller]

Well forget the "bell" :laughing:


I knew I was going to get in to rock but Hole ly COW:laughing:





I ended up with a 18" auger cuz that's all they had but I was ok with that.


I was very lucky to get through this rock today. Broke a couple of teath off the auger at some point. :confused2:


I got my 36" down and then some. :thumbsup: more like 48" in the corners.

 

[Keller]

36" seems pretty unreasonable. Takes a dang big shed to need it that big.

Here we don't fill the entire hole with crete, just the bottom thus making a "bell". Most don't even do that much. They just set the post on a cookie.

This is a 40'x100' steel building so it aint much of a "shed"