breaking ground, but will this do as pier foundation?

[gorann]

31 minutes ago, kirkster501 said:

The rock will have been there for centuries if not thousands of years and will have settled into the ground to be as solid as the rock of Gibraltar.  Leave the rock alone, scrub it so it is clean and concrete around it.  The concrete will adhere to the rock before pouring.  

I agree. That rock is unlikely to move from the gound freezing since it has had a very long time to settle. The concrete base I made for my pier was only dug down abour 50 cm on farmland and it did move a bit the first winters. Not much and easy to adjust for with polar alignments in the beginning and end of the winter. Now 5 years later there is really not much movement as it has apparently settled. Your rock has probably been there since the end of the ice age. Actually it will allow you to save a lot on concrete and the hard work of mixing concrete. So be happy with you rock! I doubt it will rock and roll.

[wimvb]

1 hour ago, RolandKol said:

Just an idea...

Maybe some local masonry or memorial headstone manufacturers would collect it free of charge?

 

1 hour ago, Davey-T said:

I guess there's no shortage of rock in Sweden, a bit that size would cost a small fortune in the UK.

Dave

Slabs of this size are "taken for granite" here. (bad wordplay joke)

You guys are welcome to collect it. Free of charge. My guess is that it weighs about 600 - 700 kg. You're also welcome to dig up any other slabs that you may find within a designated area of my property.

I've also googled a little more. The Swedish way to remove a slab of this size, or larger, is to use a chemical called slug dynamite, "snigeldynamit". It's a mixture of a powder and water that expands when it sets. It takes about 24 hours to do its job. But you still need to drill 25 mm or 1" holes into the rock.

[JamesF]

7 minutes ago, wimvb said:

I've also googled a little more. The Swedish way to remove a slab of this size, or larger, is to use a chemical called slug dynamite, "snigeldynamit". It's a mixture of a powder and water that expands when it sets. It takes about 24 hours to do its job. But you still need to drill 25 mm or 1" holes into the rock.

It's a chemical version of a plug and feathers

James

[wimvb]

58 minutes ago, JamesF said:

It's a chemical version of a plug and feathers

James

Yes, but the physical version seems fun, so I ordered a plug & feathers set. I can imagine this becoming my summer pastime. I have enough rocks to practice on. ?

[gorann]

So Wim, you are all into disintegrating that wonder of geology and completely ignore the advice from Steve and me about being happy with the boulder and use it as a super sturdy pier bottom?

[wimvb]

5 minutes ago, gorann said:

So Wim, you are all into disintegrating that wonder of geology and completely ignore the advice from Steve and me about being happy with the boulder and use it as a super sturdy pier bottom?

The boulder in itself is ok, and would be an ideal base for a pier. But it's resting on sand and clay, and may move due to frost. Plus, part of it is hanging free, and won't be much support for a pier. I will assess the situation further, and maybe take off a bit to make it more manageable, in case I pour concrete over it.

I also read threads in the Swedish astro forum. The general concensus there is that a pier base needs to be below the frost line, or needs to be insulated such that frost doesn't penetrate below it. I don't mind having to polar align on a regular basis, but if the slab drifts over time, that may cause a problem eventually. I think you're also very familiar with rocks creeping up through asfalt, in your neck of the woods. Water and frost are powerful natural forces.

If I keep the slab (which is the easiest solution), I may put a steel pier on top rather than a concrete one. That will be easier to move and adjust, if the slab decides not to stay in place.

But anyway, splitting rocks seems fun. I will split a few smaller ones to make a base for the walls.

[wimvb]

6 hours ago, gorann said:

So Wim, you are all into disintegrating that wonder of geology and completely ignore the advice from Steve and me about being happy with the boulder and use it as a super sturdy pier bottom?

Just an addendum here. That rock has been burried for ages, and was lodged between other rocks no doubt. But once I started removing those, and have dug away most of the soil around it, it is very likely to move again and eventually resettle.

But all advice considered, especially your comments Göran, I agree that it may be best to leave it where it is, and use it as a foundation for a pier. I'll make the final decision when I've cleared the rest of the obsy area.

The next two items to dig out are the fresh stump of a fir and the almost withered stump of an another, unidentified tree. I will do that this weekend.

[wimvb]

Summer pastime tools arrived.

?

[JamesF]

I look forward to seeing how well it works.

James

[Dr_Ju_ju]

I hope you have a hammer drill, capable of doing justice to those bits....

[Whistlin Bob]

On 11/04/2019 at 17:04, wimvb said:

"taken for granite"

? ? ... love a bad pun...

[wimvb]

4 hours ago, JamesF said:

I look forward to seeing how well it works.

James

Just tried on a small rock (a two man stone). Three plugs did the job, but the split was determined by the rock rather than the plugs. The edges are razorsharp. I will post pics tomorrow.

3 hours ago, Dr_Ju_ju said:

I hope you have a hammer drill, capable of doing justice to those bits....

Yes, a 500 W hammer drill. The holes need to be just 8cm deep. It only takes a few minutes to drill. But maybe the rock I tested on wasn't the hardest in the pile.

20 minutes ago, Whistlin Bob said:

? ? ... love a bad pun...

Me too. I was about to post it in "that other" thread.

[Stub Mandrel]

Chisel line of holes.

Hammer in wooden wedge, soak in water.

Worked 4,000 years ago...

[wimvb]

"First light"

More to practice on:

Enough to keep me busy:

[wimvb]

3 minutes ago, Stub Mandrel said:

Chisel line of holes.

Hammer in wooden wedge, soak in water.

Worked 4,000 years ago...

Yes, but I also got an obsy to build. ?(After all, this is in the diy observatories section.)

[JamesF]

Very impressive :)

James

[Gina]

Yes, the water soaking method is a tad slow!