Gate Post Hole Through Rock

[Obed]

Having lived in Utah and Colorado in addition to Obed's general area, I can confirm that he has sandstone, and not just sand. ...
Obed -- I think you can drill what you need to drill with a big hammer-drill and not a jackhammer. A jackhammer would just turn it into sand and pound the sand...

KentT,
You described things just as well as if you had been here. Yes, this was sandstone, not sand. I didn't know if I could get down deep enough with a hammer drill. My holes were between 15 and 21 inches deep when I hit the base sandstone. My goal was to dig the holes 3 ft. deep. Would it be possible dig down 3 ft with a hammer drill?

However, the jackhammer did just what you said; it didn't break the rock up in chunks, it pounded it into sand. Then I dug the sand out with the hand post hole digger. Then I jacked hammered some more. It took a few hours to dig 4 holes.

Obed

 

[gemini5362]

Eddie,

Remember also that the Appalachians in the Great Smoky Mtns, across the Tennessee River valley from Obed's place, are the oldest mountains in the world. This rock (if not basalt or granite) is "rotten" as it would be called in the Southwest. Even the slate and shale in this area often crumbles. However, there's marble mining and other commercial cut stone (called "Crab Orchard" stone) that's mined not far from Obed's area also... It varies widely in a pretty small geographic area.


[ Actually I have heard the same thing said about the Ozark Mountain Range being the oldest mountain range in the world. Supposedly the Ozarks were a lot higher elevation than they are now but are so old that erosion wore them down to the height they are now.

 

[Obed]

Here's a picture of the jackhammer and gasoline powered hydraulic pack. I had asked the rental place if I could hook the jackhammer up to the hydraulics on my tractor and they said no. However, after picking up the equipment, I think the jackhammer might have run off of my tractor. But using the power pack was convenient because it freed the tractor up for doing other things.

 

[Obed]

This picture shows the jackhammer bit that worked best. Notice the wide chisel like end. I first tried a pointed bit. The pointed bit just dug small holes straight down. The pointed bit would tend to get stuck in the hole and I'd have to kill myself to get it unstuck. Then I tried a chisel shaped bit that was the same width as the shaft of the bit. This bit worked about the same as the pointed bit. Then I tried the wide chisel shaped bit. This bit was the dullest so I was afraid it wouldn't work very well. However, this bit did the best job; I suppose that's why is was so dull; everyone else used it too.

 

[Obed]

Here's a hole (on the right) after finishing digging through the rock. Look at that big pile of light colored sand. All that sand was hard solid rock. If you look closely you can see a couple small rocks that came out but that was rare. Mostly the sandstone just turned to sand.

This hole will host the gate post. I hit rock at 15 inches and then dug down with the jackhammer for a final depth of just below 3 ft. I made the bottom of the holes a little wider than the tops to help resist frost heave. Making these bell shaped holes with the jackhammer wasn't a hole lot of fun.

 

[Obed]

Here's a picture of the 4 holes with the posts set in them and the 16 ft. gate after hanging it. The posts are 6x6 treated wood. Three of the posts are 8 ft long. The gate post is 10 ft. long. Getting this gate hung was a really big accomplishment for me. I've been very concerned about how I would get the post holes deep enough to hang the gate.

I hope there's a better way to dig through this rock. The way I dug the holes worked but it was much harder and slower to do than I imagined. We called several rental stores in three counties to try to rent a rock auger but nobody had one. My wife talked to a professional fence builder in our area. He said he uses a 90 lb. jack hammer to dig his post holes through rock. So maybe our method is the best way to go around here. But I'm still not quite convinced.

Maybe the hammer drill method would work better? I might run into this issue again as I think about building a pole barn sometime down the road.

 

[weldingisfun]

Here is the solution to your rock problem. But, when you see the price you'll probably pass out so be sure you are sitting down. Go to implements and then auger system. CM Trailers available at Kempner Equipment, Inc.. Your home for Utility Equipment Trailers, Gooseneck Dump Trailers, flatbed utility trailers, heavy duty gooseneck trailers, Auto Transport Trailers, livestock trailers, horse trailers, hydraulic dump trailers, heavy equipment utility trailers, Hay trailers, cargo trailers and all of your utility trailer needs. Used Trailers available. We also stock farm implements and accessories.
I've seen these things work in solid limestone. They do the job.

 

[KentT]

Eddie,

Remember also that the Appalachians in the Great Smoky Mtns, across the Tennessee River valley from Obed's place, are the oldest mountains in the world. This rock (if not basalt or granite) is "rotten" as it would be called in the Southwest. Even the slate and shale in this area often crumbles. However, there's marble mining and other commercial cut stone (called "Crab Orchard" stone) that's mined not far from Obed's area also... It varies widely in a pretty small geographic area.


[ Actually I have heard the same thing said about the Ozark Mountain Range being the oldest mountain range in the world. Supposedly the Ozarks were a lot higher elevation than they are now but are so old that erosion wore them down to the height they are now.

I've heard the Ozarks and the Appalachians were once the same mountain chain, as was the Blue Ridge and Black Mountains of North Carolina. Likely thousands of feet have eroded off the tops of them, in addition to rivers (such as the Mississippi or Tennessee) cutting through them. The Cumberland Plateau (where Obed lives) is very similar terrain as the parts of the Ozarks that I've visited.

KentT,
You described things just as well as if you had been here. Yes, this was sandstone, not sand. I didn't know if I could get down deep enough with a hammer drill. My holes were between 15 and 21 inches deep when I hit the base sandstone. My goal was to dig the holes 3 ft. deep. Would it be possible dig down 3 ft with a hammer drill?

However, the jackhammer did just what you said; it didn't break the rock up in chunks, it pounded it into sand. Then I dug the sand out with the hand post hole digger. Then I jacked hammered some more. It took a few hours to dig 4 holes.

Obed

Obed, I have similar rock in some places around where my property is next to Townsend on the other side of the valley. It's usually a pale, golden yellow, but will sometimes be off-white or even a bright white.

When I built the driveway into my lot, we hauled a dozen tandem loads of fill-dirt from just a couple miles down the road, where a guy was cutting off the hillside behind his house to change the drainage. It was bright orange/red clay filled with "nodules" of white sandstone. Here's a pic of the truck dumping a load as we were installing the culvert. Though they look like clumps of clay, they're actually clumps of sandstone covered in clay. I gathered up quite a few of them to use as "rip-rap" around each end of the culvert, and to build a small catch-basin at the lower end of it. Some of those nodules would literally fall apart in my hands. I found it quite interesting that these were intermixed in the clay hillside -- and didn't run in layers or veins. It was like they were "seeds sprinked through the dirt." It's also interesting to note the contrast in the soil type -- from less than two miles away. My dirt appears to be decomposed shale and organic material and is a light yellowish-brown when the organic stuff is removed...

http://farm1.static.flickr.com/43/108509319_2669e9009b.jpg?v=1142118739

http://farm1.static.flickr.com/45/111052493_7fb8ba1c95.jpg?v=0

http://farm1.static.flickr.com/36/108514017_6179c35180.jpg?v=1142119772

As far as using a hammer-drill, I've seen holes dug in this stuff by drilling a ring of smaller, shallow holes, then using a long pry-bar to break out the soft rock between the holes. Then you repeat the process -- similar to chiseling out a mortise joint in large timbers... Don't know if it is really faster or easier than what you did, but as they say "Necessity is the mother of invention...."

 

[Zinno87]

I've yet to try this roduct on my own, but it seems like it does have a lot of potential. It's more for freestanding rock, where there is room for the material to expand, but I'm curious as to whether it would have worked well enough for an application such as yours. You'd probably have to drill a few holes in the rock, pour it in and wait. After that, you might be able to get the fractured pieces of rock out, assuming they fracture, with a regular auger.

Welcome to Archer Company USA, Inc.

 

[EddieWalker]

Obed,

Congrats on digging your holes. Nothing better then setting a goal and achieving it!!!

Eddie