wroughtn_harv
Super Member
Belling is done with a special drilling tool. Basically you have two wings, one on each side, that come out and they are hinged at the top.
Imagine a piece of pipe with a trap door bottom. Now think of two wings or cutting blades hinged at the top. The hinge slides up and down in slots.
When they bell they usually have two drilling trucks on the job. One drills down the pier and the other has the belling attachment. The pier is drilled and then bell rig goes to work. He places the bell on the bottom of the hole. He puts down pressure and then spins the tool. The down pressure causes the wings to come out cutting a bell shape. The operator knows by experience when the tool is full of dirt. He brings it up, rotates away from the hole, a helper releases the bottom and empties the tool. This is repeated until the hole is belled.
The reason the holes are belled is because the pier is needs to not only hold the structure up it is also needed to keep it from lifting. Expansive or clay soils require piers that do this. Right now foundation repair is the business to be in. That's because the drought has caused the clays to dry up and shrink. Everything is falling. We're seeing 1 foot plus deep depressions in some places. If your house is sitting partially on one of those depressions you have a good chance of having a broken foundation if you don't have good belled piers beneath your house.
There are all kinds of foundation repair schemes. The best one I know of involves two piers drilled at angles with a common haunch. Think of an upside down V. These replicate what happens with a belled pier without having to tear down your house to get a truck in to drill the piers because it takes a lot of crowd or down pressure to operate a belling tool.
Those schemes without the belling principle involved do a lot of adjusting forever. As the seasons and water content changes they become inefficient and have to be re-torqued to be effective.
Three feet deep piers unless they are in rock are fence post holes. If you are in expansive soils like we have in north Texas you might be talking 16" piers that are belled 20 plus feet deep on ten foot centers. The latest foundation scheme that makes the most sense to me involves excavating the soil with a front loader crawler to ten feet deep. You will have gone through a couple of layers of different soils. The soils are mixed with the loader on top and then replaced back into the cavity and packed in according to a schedule with water. Then the pier trucks come and drill the piers.
It isn't rocket science but if you can imagine removing your furniture, your floor coverings, and then having a crew bring in equipment to properly drill piers because you didn't before hand it does make sense. That's on the inside, you might have ten of these. On the outside you might have thirty piers placed, landscaping has to all be redone. Foundation issues aren't covered by insurance.
Imagine a piece of pipe with a trap door bottom. Now think of two wings or cutting blades hinged at the top. The hinge slides up and down in slots.
When they bell they usually have two drilling trucks on the job. One drills down the pier and the other has the belling attachment. The pier is drilled and then bell rig goes to work. He places the bell on the bottom of the hole. He puts down pressure and then spins the tool. The down pressure causes the wings to come out cutting a bell shape. The operator knows by experience when the tool is full of dirt. He brings it up, rotates away from the hole, a helper releases the bottom and empties the tool. This is repeated until the hole is belled.
The reason the holes are belled is because the pier is needs to not only hold the structure up it is also needed to keep it from lifting. Expansive or clay soils require piers that do this. Right now foundation repair is the business to be in. That's because the drought has caused the clays to dry up and shrink. Everything is falling. We're seeing 1 foot plus deep depressions in some places. If your house is sitting partially on one of those depressions you have a good chance of having a broken foundation if you don't have good belled piers beneath your house.
There are all kinds of foundation repair schemes. The best one I know of involves two piers drilled at angles with a common haunch. Think of an upside down V. These replicate what happens with a belled pier without having to tear down your house to get a truck in to drill the piers because it takes a lot of crowd or down pressure to operate a belling tool.
Those schemes without the belling principle involved do a lot of adjusting forever. As the seasons and water content changes they become inefficient and have to be re-torqued to be effective.
Three feet deep piers unless they are in rock are fence post holes. If you are in expansive soils like we have in north Texas you might be talking 16" piers that are belled 20 plus feet deep on ten foot centers. The latest foundation scheme that makes the most sense to me involves excavating the soil with a front loader crawler to ten feet deep. You will have gone through a couple of layers of different soils. The soils are mixed with the loader on top and then replaced back into the cavity and packed in according to a schedule with water. Then the pier trucks come and drill the piers.
It isn't rocket science but if you can imagine removing your furniture, your floor coverings, and then having a crew bring in equipment to properly drill piers because you didn't before hand it does make sense. That's on the inside, you might have ten of these. On the outside you might have thirty piers placed, landscaping has to all be redone. Foundation issues aren't covered by insurance.
. Dig your hole close to the depth, scrape the bottom flat, set the big foot and sonotube plumb and to your line. You can set them with small batter boards and drywall screws. Backfill carefully so as not to disturb. Run a laser level and put a screw in at that point and pour to that level. They go quickly after the first couple and work very well.