Shaft Ice Annomalies

[flintgreasewood 38]

Ever since last summer when I was removing ice from my prospect shaft I have been puzzled by something I found.  I was down probably about 25' jack hammering away when suddenly I was blasted by pressurized water.  Immediately I figured I had broken through into the old drift.  Unfortunately, that was not the case.  At that point I was not even half way to the bottom of the shaft.

So what was going on with that water pocket which was surrounded by solid ice and frozen muck walls?  Actually, it was not the only pocket I hit.  There were a couple more though neither was pressurized.  Anyone have any ideas?

[Eric N 22]

Only a guess.

Water doesn't pressurize so there had to be some air trapped as well.

As water freezes, it expands just a scoosh. 1.00013 unit volumes of water at 32°F expands to 1.00186 unit volumes at 14°F. (From CRC Handbook)

Not a lot of expansion, but it busts engine blocks, cracks pump housings and just causes general havoc for the procrastinator.

So imagine the ice freezing in a shell inside the shaft. It has some air trapped inside the shell. As temperature drops, the ice expands in the only direction it can, into the area where the air is trapped. This might explain why only one was pressurized.

But I'm just guessing.

eric

[flintgreasewood 38]

I get the pressurization theory but why wouldn't the freezing of the water in the pocket be inexorable and the pressurized air merely fracture the surrounding ice and dissipate into it?  Could it be that even after 100 years of freezing that there was just still a little bit of water left and given a few more years it too would have frozen?  Dunno!

[Geowizard 122]

One of the "variables" is chemical composition. Since we know it isn't "pure" water, it may contain salt(s). Common salt is sodium chloride. There are many other salts that can affect the temperature at which water freezes.

 

IF you take salt water and freeze it, water will begin to crystalize and in it's crystalline form, is H2O. The remaining liquid becomes more saturated with sodium chloride. The higher the saturation of sodium chloride, the lower the freezing temperature.

 

So, consider that the surrounding muck was frozen at a temperature slightly below 32 degrees F and the isolated brine (salt solution) was at the same temperature and was not cold enough to freeze.

 

Another possibility is that the hole is deep enough and that as you approach the "mantle" it becomes warmer. But... that's probably not the case!

 

- Geowizard

[Geowizard 122]

I just had another thought... (hydrology 101)

 

You are excavating in the "vadose zone". The surface of the earth contains surface run-off water from snow melt and rain and that run-off finds channels (water courses) that extend vertically downward. That process forms and recharges "aquifers".

 

Alaska is known for earthquakes. Earthquake activity could cause fractures in the frozen solid terrain. The fractures represent channels that surface waters run into and that water could migrate to substantial depths.

 

- Geowizard

[Geowizard 122]

I thought up another possibility.

 

Nearby creeks and rivers cross sections of bedrock that are fractured and faulted.

 

Fractures in bedrock occur in all forms, vertical, sub-vertical, north, south, east and west. Fault zones and fractures in bedrock are pipelines for water. The elevation of mountainous terrain miles away, provides "tank" pressure. Tank pressure amounts to approximately 0.4 psi per foot of elevation. Now, also consider the fact that you are sinking a shaft vertically. The shaft adds 0.4 psi for each vertical foot of drop. A nearby water source elevated 100 feet above the collar of your shaft could provide a source of bedrock water that has 40 psi (household) pressure.

 

- Geowizard

[Geowizard 122]

Because you are finding water pockets, it is probable that you are approaching bedrock (read the post above). If you are approaching a pressurized bedrock "pipeline". caution should be observed. Shaft sinkers are all too painfully aware that they possibly could intersect a pressurized fracture that will fill the shaft quickly.

 

- Geowizard

[flintgreasewood 38]

Chuck,

   Interesting concepts.  The saline idea is intreguing.  Threre was so much "stuff" in the liquid, very brown in color and completely unlike the clear ice surrounding it.  That first pocket, and the only one that was pressurized, was a long ways from bedrock.  I've heard of miners being rapidly flooded out of a drift upon breaking through into an underground stream, but I don't know if that ever happened in permafrost unless they were in a zone of intermittent permafrost.

[Eric N 22]

If the water was from a groundwater system ala artesian, then it would have kept flowing.

Brown water can be indicative of surface waters carrying tannin from vegetation.

Most of us that have spent much time in the north country are familiar with frost cracking of the ground. Now imagine warmer water (36°F is warmer than ice) running into one of these frost cracks. The channel it erodes won't be uniform and is probably seasonal in existence.

Okay, here I really going out on the guessing limb. Falling water drags along air. The odd shaped channel eroded by water allows some of the air to be trapped. For a great example of this process, do a web search for trompe+ventilation. Here is one example:

http://tcpermaculture.blogspot.com/2012/11/the-trompe-almost-forgotten-air.html

Here is a slide show for air trompes:

http://www.slideshare.net/MichaelHewitt4/leavitt-2013-amr-trompe

But I'm still guessing. Just consider this comment as nothing more than an introduction to a bit of arcane mining history.

eric

[chickenminer 42]

Could it be you hit a pocket of water and your "pressure" came from the jack hammer bit ?

 Was this a little squirt, or a lot of water ?

 

 I know after I put a fire in a hole and go to muck it out, if there is any water left in the bottom

it makes using the pick nasty. Seems water runs into the pick depression and on the next swing

when that pick hits the same depression .... well, displaced water has to go somewhere and in a hurry.

 Could be same thing with your jackhammer.

[flintgreasewood 38]

No, Dick...it was a lot of nasty, smelly water.  I was hit with probably a couple of quarts and there was a lot more left in the cavity.  The pressure was so great that it blasted my face and I'm almost completely upright when jackhammering.   I should also add that it was in the center of the shaft ice...about 16" from the muck wall.

[Rod Seiad 28]

Water? nah it was natural anti-freeze which was part water containing a strong brew of surface components.

Did you taste it? salty? bitter? sweet? warm?

It's temperature, PH, salinity and volume would need to be tested inorder to figure it out. 2 quarts 25' down should've been solid not liquid.

You could patent that stuff.

[flintgreasewood 38]

Rod, you may have something there.  I remember when I worked up in northern Wisconsin during my high school summers, we'd set aside containers of "bug juice" or cool aide type drink before we'd leave at the end of the season.  It would ferment and then freeze during the cold winter.  But it wouldn't freeze solid.  There would be a core of liquid that was almost pure alcohol. 

Can't say that I checked the alcohol content of my shaft brew.  Maybe that's the source of Alaska Amber Ale...filtered, of course.