Use of a metal detector to find large rocks?

[sdef]

In the foreseeable future I will be fencing in a 1 acre garden area off the back of the house. With all of the rocks on my property I have decided not to use wooden 4 x 4 posts except at the corners and gates (or possibly metal pipe) and use T-posts everywhere else. From responses to a previous post, I will probably use a #5 driver bucket attachment from bucketdriver.com

My property is VERY rocky and it is quite a chore just to get the driveway flat enough to lay gravel. It seems that every 4" - 6" hump in the ground is only the tip of the proverbial iceberg and I have to dig up the large rock which usually seems to be surrounded with smaller large rocks. I have attached two pics for those who have not seen previous posts of my rocks and I have dug up quite a few rocks like the largest one and a huge number of smaller rocks in the 20# - 100# category, along with quite a few between 100# and 300# or so. A lot of it is granite.

Since I do not have access to a ground penetrating radar unit to make my fence post positioning easier, I am wondering if a good quality metal detector would be helpful? It sounds like a good idea to me but I have never used such a device. Any comments from those experienced with metal detectors or any other ideas would be appreciated. I am planning on driving the posts ~ 2 feet deep.

 

[bcp]

Mine doesn't seem to find a difference between rocks and dirt. It might with the right settings and a rock of the right type, but it won't on my land.

What I have done, at a couple of places where I kept hitting rock, was to drive a small, smooth rod (1/4, 3/8) where I wanted a post, to see if it would go in to my desired post depth.

Bruce

 

[sdef]

Mine doesn't seem to find a difference between rocks and dirt. It might with the right settings and a rock of the right type, but it won't on my land.

What I have done, at a couple of places where I kept hitting rock, was to drive a small, smooth rod (1/4, 3/8) where I wanted a post, to see if it would go in to my desired post depth.

Bruce

Thanks. Odds are most detectors would be the same since they all use similar technology. I may have to drive a section of rebar first as a test.

 

[bcp]

Rebar is harder to drive and pull, I found.

Bruce

 

[/pine]

look for a "ground probe" with a T handle...

 

[sdef]

look for a "ground probe" with a T handle...

/pine: Something like this? My ground is very hard clay and very difficult to dig in using a new, Bully Tools pointed shovel. I am wondering if I will be able to manually drive this down 24" or not. Thoughts?

Amazon.com: PlumBest P27005R3 60-Inch Steel Probing Rod, Black: Home Improvement

 

[kebo]

I have been using metal detectors for many years now. They are obviously designed to locate metal objects, not rocks or dirt. The higher end models with a ground balance control can sense differences in the density of the soil, but I think trying to interpret the differences in the tones when moving from all dirt to a large rock (buried under the soil a few inches) would just eventually lead to frustration with it. I don't think you could accurately learn to distinguish the difference, on a consistent basis. The tradeoff though, is that you might find some really cool metal stuff with it lol.

 

[sdef]

I have been using metal detectors for many years now. They are obviously designed to locate metal objects, not rocks or dirt. I don't think you could accurately learn to distinguish the difference, on a consistent basis. The tradeoff though, is that you might find some really cool metal stuff with it lol.

Thanks. You guys have burst my bubble and saved me some money on a tool that would not have worked for my purposes. I was hoping a metal detector would zone in on the mass of the rocks and differentiate between rock and earth, but apparently not. However, around here there supposedly used to be some gold mines years ago and some say that where a lot of granite is found, so might be gold... So maybe I could retire if I bought one, maybe ??? Ha, ha. Even I can't justify this... and I can justify a lot.

 

[BukitCase]

After looking at your pix, I think I'd be more tempted to find a used rock crusher and start a gravel business - then you could use the profits to truck in REAL soil and try to forget what's under it...

Holy crap, a "leave-rite" farm AND clay - man, you musta REALLY done somethin' rotten in a past life

Seriously, I'll probably never complain about my nearly rock-free clay soil again... Steve

 

[sdef]

After looking at your pix, I think I'd be more tempted to find a used rock crusher and start a gravel business - then you could use the profits to truck in REAL soil and try to forget what's under it...

Holy crap, a "leave-rite" farm AND clay - man, you musta REALLY done somethin' rotten in a past life

Seriously, I'll probably never complain about my nearly rock-free clay soil again... Steve

Oh man. The whole place is like this and looks nothing like typical SC or Ga soil. Long story short, the place would not perc for a septic tank- which I knew when I purchased it as I had the country test it. So we hired a soils engineering firm out of Charlotte, NC, along with a guy and a mini-x to help as a last ditch effort to find percable soils, (which we actually did and got approved for a 4 BDRM, 4 Bath home) before we invested in an engineered septic system ($20k - $25k). When the engineer met me on the property, he was absolutely amazed at the soil type and stated he had never seen anything like this before and took some photos to show his coworkers.

Just a few of the rocks from the driveway used for landscaping that has grown 50% since these pics were taken:

 

[oosik]

Well--- that is a lot of rock, BUT there is enough soil to grow trees. With the correct implement on your 3-point you should be able to build a large rock wall and have a garden site, all at one time. It will take time but in the end it will work and it will be all yours.
My soil is almost rock free - it just that about 1/4 of my property is exposed basaltic lava. I grow moss on top of that lava, :laughing: :cool2:

 

[Depmandog]

The probe you referenced looked to be pretty substantial, and I would guess it would be a real chore trying to push that 24" into your soil. I think what the others were thinking was a solid rod about 3/16" in diameter about 30" long with a T handle.

What might be the easiest is a 24" long auger bit and a cordless drill. Wouldn't spend much on the bit, it will be ruined. Once you make it full length, spray a mark across the hole with some flagging paint.

Hope you got your place for a steal...lots of work in your future de-rocking that place!!

 

[sdef]

The probe you referenced looked to be pretty substantial, and I would guess it would be a real chore trying to push that 24" into your soil. I think what the others were thinking was a solid rod about 3/16" in diameter about 30" long with a T handle.

What might be the easiest is a 24" long auger bit and a cordless drill. Wouldn't spend much on the bit, it will be ruined. Once you make it full length, spray a mark across the hole with some flagging paint.

Hope you got your place for a steal...lots of work in your future de-rocking that place!!

Yes, got a great deal on it as the bank owned it. And this was the only place that met our location and amenity requirements after many months of looking and dealing (on this one.) It is in a small country subdivision of 3.3 to 20 acre lots and ponds, surrounded by farms. The back half of the property is far less rocky and I am going to leave this front half as it, except for the driveway.

I like your idea of the drill and auger. With my soil type this is probably the easiest and quickest way to locate fence posts sites. Will have to purchase of bunch of bits, I imagine

 

[sdef]

I think I found the right drill bit(s) to use. It would be great if I could use a hand auger, but think my property would rebel.

MAGBIT 781.24.0816 MAG 781 1/2-Inch by 24-Inch Carbide Tipped Bellhanger Drill Bit - Installer Drill Bits - Amazon.com

 

[Gary Fowler]

I think I found the right drill bit(s) to use. It would be great if I could use a hand auger, but think my property would rebel.

MAGBIT 781.24.0816 MAG 781 1/2-Inch by 24-Inch Carbide Tipped Bellhanger Drill Bit - Installer Drill Bits - Amazon.com

I think that is exactly what you need. You may need to invest in extra batteries for your drill. You are likely going to be drilling a lot of holes. Get some flags to put in when you do manage to get a hole down. T Post might go in if you find a 1/2 clear space, but don't count on getting an auger to go as there are likely many more rocks to the side that you may hit. For corner post, a back hoe to get out all the rocks is likely the only way, then you can back fill around the post with all the rocks you removed. It should be just as tight as putting concrete around it when properly compacted. Maybe some quick-crete (dry) dusted around the rocks to fill in the spaces also. The soil should then have enough moisture to harden the concrete.