how hard to dig 50 feet underground

[binabik]

I don't know anything about digging holes to put say 5 stories underground and was wondering how hard it is to dig two different sized holes.

these will be open to the top and at least this big, all the neccessary infrastructure for the machines to go in and out or anything.

first hole is 50 feet deep, 400 feet wide, and 400 feet length.

second hole is 50 feet deep, 400 feet long and 40 feet wide

it can be bigger if need be i just need to know how hard this would be to dig, maybe how much it would cost and the vehicals that might be needed, though the difficulty is the main thing though.

P.S. This does have something to do with archetecture i just don't feel like talking about it yet.

[Moontanman]

Originally Posted by binabik

I don't know anything about digging holes to put say 5 stories underground and was wondering how hard it is to dig two different sized holes.

these will be open to the top and at least this big, all the neccessary infrastructure for the machines to go in and out or anything.

first hole is 50 feet deep, 400 feet wide, and 400 feet length.

second hole is 50 feet deep, 400 feet long and 40 feet wide

it can be bigger if need be i just need to know how hard this would be to dig, maybe how much it would cost and the vehicals that might be needed, though the difficulty is the main thing though.

P.S. This does have something to do with archetecture i just don't feel like talking about it yet.

How hard it would be to dig a hole, any hole is directly related to where you dig the hole. How hard is the soil/rock and how high the water table is. Where I live it would close to impossible to dig a hole that big, water and sand would wash in continuously until all you have was a large pond with sloping sides!

[binabik]

well i don't know where it will be but let's say it is above the water table the whole time and i have the best equipment for the job and feel free to list all types of soil and rock, i really just need a simple answer compared to other types of big holes. what i am planning, though no formal training and i doubt the idea will ever come to fruition, is to dig the hole and then drop some prefab units in there of my own design

EDIT: Oh and i am then gonna cover it back up

[Moontanman]

Originally Posted by binabik

well i don't know where it will be but let's say it is above the water table the whole time and i have the best equipment for the job and feel free to list all types of soil and rock, i really just need a simple answer compared to other types of big holes. what i am planning, though no formal training and i doubt the idea will ever come to fruition, is to dig the hole and then drop some prefab units in there of my own design

EDIT: Oh and i am then gonna cover it back up

I'm not an engineer but I would have to assume that sand would be easiest to dig up and granite or basalt would be the most difficult. I've given some thought to building under ground but you would really have to decide where and then adapt to the physical characteristics of your site. The variables for every type of situation would be far too large to list.

[Thunderbird]

When my father and I wanted to dig a big hole on the property we dug holes with post hole diggers down to 4' place a large coke cup, 32 ounces, filled with SLURAN basically it's fertilizer and fuel oil mixed together, embedded within the sluran, a TNT primer cord, a blasting cap on the end of 5 feet of waxed fuse.
Now here’s the fun part, after filling in the hole with the explosive , place the largest and longest green oak log you can find upright over the hole. Yell fire in the hole!!! Light the fuse, and walk, don’t run to a safe distance, 100 yds behind the truck. What you see is a sudden red jet of clay shoot up along with muffled BUMP sound instead of a boom. The log redirects the explosion down further and excavates a rather large hole. The fun part is watching the 400pound log slowly turning 300-400 ft in the air before falling back to earth.

[modest]

In all likelihood you'll hit bedrock before 50 feet. So, moontanman is right, this all depends on the particulars. If you're building a foundation and need to hit bedrock then this would be no more expensive than any normal excavation. If you need the whole 50 feet and you've incidentally got bedrock in the way then the cost would be enormous. What kind of bedrock, how thick, ect depends on the site and could not be properly priced without a civil engineer or contractor doing a proper inspection. How much does it cost to dig a 400 x 50 foot hole just isn't so easily answered.

~modest

[TheBigDog]

If you are going to bury it, then you may not need to dig the full 50 feet. What you put in the hole will take a great deal of the excavated space, and the dirt you removed would pile on top. A structure 50' high may only need a 30' hole to be buried under a mound of the excavated material.

What are you cooking up, anyway?

Bill

[Zythryn]

Also keep in mind the structure will be under pressure/weight from the surronding earth and the earth on top of it.
Some expense will likely be incurred to support the hole as it is being dug. Unless it is bedrock most dirt will not support a very deep hole.

[DFINITLYDISTRUBD]

And as you go deeper you will need to excavate some form of ramp for the vehicles being used to dig and haul the earth outoutside of the hole...short of using a dragline excavator this is a must...in the case of using said excavator be prepared to shell out several million dollars just to obtain it and have it built on site (no digging yet just purchase and setup) followed by a few thousand dollars for fuel and a few tens of thousands more for labor. (Oh yeah be prepared to wait a couple of years for the draglines components to be manufactured) Odds are using more conventional equipment is just as expensive but would probably be somewhat quicker (a few months vs. a few years). So a few million.

[Moontanman]

Maybe it's a giant end of the world shelter?