holes drilling (digger size)

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aucklander

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# 251131 10-Jun-2019 12:42

Hi,

I am heading into a larger project, which at some point will require drilling for deck piles at approx 4.7m depth at 400mm diameter. Why they are that deep is not the subject of the post - but I had discussions with various earth moving companies and they have very different views on the digger size required for such task. One says a 5T will do it, others want to bring a 30T digger on site!

I saw a 30T digger at a petrol station nearby which gets the underground tanks replaced - and let me tell you - that machine looks huge! I really do not want that on the driveway (especially on a shared driveway)...

Is there any way to get access to this sort of info? How is a digger size selected based on hole diameter and depth? I will not start to argue with the contractors but I want o get some confidence in the solutions they propose. Of course they all exclude any responsibility for concrete surfaces (or any damage to the property whatsoever).

Thank you.

ObidiahSlope

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# 2255233 10-Jun-2019 13:02

Have you considered using the sucka truck method or as it is technically known hydro excavation?

This technique uses a high pressure water jet to loosen the material which is then sucked into a truck mounted vacuum tank.

It causes less ground disturbance than a digger and is the preferred method where there may be existing underground services.

Obsequious hypocrite

wellygary

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# 2255286 10-Jun-2019 14:04

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Are you planning on landing planes on this deck :),

I'm guessing they are concerned that the smaller machine will not have enough hydraulic power to run such a big Auger to get through hard earth/rock in the bottom bits of you holes, -

As for the suggestion of Hydro excavation, its good for volume excavation, but its hard to prevent the hole "ballooning" at the bottom which then requires a boat load more concrete to fill in (lots of extra $$$)

larknz

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# 2255311 10-Jun-2019 14:37

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Have you talked to any well digging contractors. They may have suitable truck mounted augers.

Fred99

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# 2255338 10-Jun-2019 15:10

aucklander:

Why they are that deep is not the subject of the post

OK - but I have to ask. Why do you need 4.7m holes?

That seems extremely extreme.

But if that's what you need, talk to contractors who do retaining walls, digging very deep holes for high retaining wall poles in residential area is reasonably routine.

They'd usually put rubber tracks on the digger if they're going up a residential driveway. The concrete trucks you'll be needing will probably weigh more than the digger.

DarthKermit

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# 2255341 10-Jun-2019 15:12

Fred99:

The concrete trucks you'll be needing will probably weigh more than the digger.

And are virtually certain to break a residential driveway.

Fred99

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# 2255370 10-Jun-2019 15:52

DarthKermit:

Fred99:

The concrete trucks you'll be needing will probably weigh more than the digger.

And are virtually certain to break a residential driveway.

Yeah - quite possibly. OTOH, they might be able to set up on the road and pump the concrete.

Jase2985

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# 2255380 10-Jun-2019 16:07

Something like this work?

http://www.bladepile.co.nz/

nickb800

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# 2255416 10-Jun-2019 17:21

If you are genuinely into big digger territory, then perhaps something else instead of traditional piles like screw piles might become cost competitive.

If it's easy digging ground, can you use a post hole borer with several extension pieces?

JeremyNzl

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# 2255463 10-Jun-2019 17:45

Hi,

Sometimes the larger the machine you can put on the job the more productive it will be,

Some caveats

30 ton digger will probably need a piloted transporter extra cost.

20ton digger no pilot cheaper delivery.

4.7m is quite a hole, depending on the ground being drilled casings may be required. if the ground is stoney or very hard, extra horsepower would be required.

a 5ton digger may not be suitable as its reach with the auger drive on the end would not be able to lift the auger at depth out of the hole.

but would happily drill a 400mm hole but would require auger segments to be added and removed.

anything larger that an 6ton would be preferable provided it has 5.5m - 6m of reach, assuming auger drive and drill are that lengths.

then it can do it in one hit.

Check out pilehire.co.nz and give them a ring if you want some qualified advice, I brought an 800mm auger from them last year they were great to deal with.

20ton+ diggers will make a mess of light concrete and roads due to weight.

Hope that above is of some help,

Cheers Jeremy

aucklander

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# 2255859 11-Jun-2019 10:39

JeremyNzl: "a 5ton digger may not be suitable as its reach with the auger drive on the end would not be able to lift the auger at depth out of the hole.

but would happily drill a 400mm hole but would require auger segments to be added and removed"

one of the earth moving guys also mentioned the reach being too small on a small digger... which I never understood why is an issue, I never expected them to drill the whole thing in one hit, you need to get in and out every 300 - 500mm anyway to remove that "plug" of soil, then advance another bit, so you get in and out a lot of times, from a certain point you just start to use extensions. Of course it is more time consuming as you need to install / remove them every time, but that does not mean you need to get there a larger digger and destroy the driveway only because they need to save few hours on site... I would happily pay for their extra hours rather than the $20k bill for the driveway after that...

I ma still trying to get an idea if screw piles will require smaller digger than drilled piles... I contacted Pilehire, thank you for the lead, will see what they think too.

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wellygary

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# 2255867 11-Jun-2019 10:49

aucklander:

one of the earth moving guys also mentioned the reach being too small on a small digger... which I never understood why is an issue, I never expected them to drill the whole thing in one hit, you need to get in and out every 300 - 500mm anyway to remove that "plug" of soil, then advance another bit, so you get in and out a lot of times, from a certain point you just start to use extensions.

The problem is not going down, its at the end when you have to pull the pull the full length of all the extensions out.... It needs to be done in one lift..

if you are forced to disconnect the extensions one by one, when you uncouple the first one the lower ones will fall back to the bottom of the hole, ( and for a 4.7 metre hole that spells trouble)