Spar Mine (Hendre)

[Ian A]

[quote="cavefrog" post=2637]Great pics again Ian, I love the cave pearls, erm and i'm glad the spider pic never made the cut (I had nightmares about a spider last night - no kidding).[/quote]

Sadly, no, the spider did not come out - my photographic talents are not yet on par with my peers :S

Sorry you had nightmares but, on the positive side, there are far worse things to ponder over :silly:

Ian

[Ian A]

[quote="martymarty" post=2638]still gonna kick your ass ..shortstuff[/quote]

Heard it all before .. blah blah de la de dah blah .....



Ian

[John Nicholson]

Several questions....
I am puzzled by some of the pictures above as they seem to be taken in a different mine to the Hendre Spar mine I have now explored on several occasions.  

Is the level of water now falling at a slower rate?  It seems to me that the level dropped at about 10" a week when the water filled the whole lower chamber - a huge volume.  But now the water level just reaches the top of the incline, so in theory the water level should fall more rapidly if the rate of drainage volume is constant.  But the level of water in the incline does not seem to be going down much at all.

Has anyone measured the depth of the mine from the entrance hole down to the floor level of the lowest level now accessible?  Has anyone experimented with an altimeter to measure the depth of mines?

I am intrigued by the thick sticky texture of the clay like mud that now covers the lower level - as shown in one of the pictures above.  This is probably formed by the precipitation of very fine particles in the flood water. Has anyone explored the use of this sort of mud as a modelling pottery clay for firing?

Comments welcome...

[Ian A]

My only comment is with regard to the receding water ....

We do not know why the water is dropping but have "guessed" something may have opened up allowing water to drain.

Assuming that is the case (and it may not be) the water may slow down it's rate of drain as it reaches the escape as the water pressure will fall or, it may become partly plugged with debris slowing it down.

It may not be a "Plug" in any event .....

Additionally, I am not certain the rate is slowing as, from Marty's pictures on facebook, the water has very clearly dropped significantly in the last two weeks (The deepest part where there "party" is stood is only ankle depth and Dylan was wading up to his waist there on my last trip 2/3 weeks ago.

[Tim Watts]

[quote="JohnNicholson" post=3566]Has anyone experimented with an altimeter to measure the depth of mines?
[/quote]

yes, - but only the rather crude one thats built into my watch. Obvious potential problem being that in a system where the pressure variations caused by the cooling/warming of areas (i.e. anywhere where you have a draft meaning air moving from a higher pressure area to a lower pressure area) are going to influence the measurement. To add to this humidity changes also play a large part in the equation.

As can be seen from the relationship between p (measured atmospheric pressure) and h (the height in meters above sea level):


p = Po * ( 1- ( (L*h)/To ) ^ ( (g * M)/(R * L) )

Where:
Po = Standard Sea Level atmospheric pressure (101325 Pa)
L  = Temperature Lapse rate (0.0065 K/m)
To = Standard sea level temp (288.15 K)
g  = acceleration due to gravity 9.81 m/s^2
M  = Molar Mass of dry air (0.0289644 kg/mol)
R  = Universal Gas Constant 8.31447 J/(mol.K)


In large open mines - like this one - its much more likely to be accurate though :-) And lets face it, the degree of accuracy may/or might not been deemed good enough depending on what you're doing.

[Tim Watts]

[quote="TimWatts" post=3573][quote="JohnNicholson" post=3566]Has anyone experimented with an altimeter to measure the depth of mines?
[/quote]

yes, - but only the rather crude one thats built into my watch. Obvious potential problem being that in a system where the pressure variations caused by the cooling/warming of areas (i.e. anywhere where you have a draft meaning air moving from a higher pressure area to a lower pressure area) are going to influence the measurement. To add to this humidity changes also play a large part in the equation.

As can be seen from the relationship between p (measured atmospheric pressure) and h (the height in meters above sea level):


p = Po * ( 1- ( (L*h)/To ) ^ ( (g * M)/(R * L) )

Where:
Po = Standard Sea Level atmospheric pressure (101325 Pa)
L  = Temperature Lapse rate (0.0065 K/m)
To = Standard sea level temp (288.15 K)
g  = acceleration due to gravity 9.81 m/s^2
M  = Molar Mass of dry air (0.0289644 kg/mol)
R  = Universal Gas Constant 8.31447 J/(mol.K)


In large open mines - like this one - its much more likely to be accurate though :-) And lets face it, the degree of accuracy may/or might not been deemed good enough depending on what you're doing.[/quote]

Obviously all that is required normally is a dP i.e. the difference in absolute pressure measured at point x and point y within the mine, in order to give a height and providing there is no major changes in humidity or thermally induced pressure variations between these points then it should be pretty much bang on.

[Ian A]

When I am underground I take it forgranted that I am underground.

That tends to be sufficient :huh:

Ian

[Tim Watts]

Ahh, but what if you are alone, and you turn off your lamp and you are in utter utter darkness. Where are you then?? ;-)

[Ian A]

[quote="TimWatts" post=3576]Ahh, but what if you are alone, and you turn off your lamp and you are in utter utter darkness. Where are you then?? ;-)[/quote]

In solitude :huh: :huh:

[John Nicholson]

My reason for asking about the depth of Hendre Spar mine is because it seems to me that the distance we drop down through all the shafts by ropes and ladders is greater than the distance we climb up from the car park. In just want to get an idea of the level at which the mine was operated - and also how far into the mountain it extends.  It would all be answered by mapping.

If the water is draining out then it is probably not draining into the rive - because there is not a river.  It has already disappeared underground.  I assume that the river actually drains to Milwr.  So the water in Hendre Spar mine will also be finding its way to the Milwr.  How far down is that?  Are there known links from this area to Milwr?

[Ian A]

The Milwr Tunnel is approx 440 feet below the road level and there is a link to it from Garreg Boeth which is only a field or two away from the Hendre Spar Mine.

I personally don't know the depth of the Spar mine but we have seen a further flooded incline (decline) with a divers line attached so there is yet more to see.

Someone, somewhere will have a plan of the mine system

Ian

[John Nicholson]

Yes - there is a map (I assumed was drawn by Ian) at the beginning of this article, but now very out of date.  But it is a diagram in plan for each floor.  It would be interesting to see this mine in longitudinal section.

[Frank Hill]

John
I intend to take my paragliding altimeter into the mine the next time I go.
I'll let you know the outcome.

[John Nicholson]

That would be brilliant! It would be useful to have a reading at the car park and also at the place where the sheds are at the bottom of the incline.
There is a lot I still don't understand about this mine.  Why did the miners draw their spoils UP the underground inclines from low levels, instead of driving the levels horizontally to the surface?  Also where is the other part of the mine with an unflooded incline and a big chamber with machinery and a railway on a lower level?  Or is this a different Hendre Spar mine?

[Frank Hill]

I think the incline you are speaking of is down the first ladder to a lower level then you have to go through a small hole and abseil (SRT out).
THis is the incline that I reckon connects somehow to the flooded passage Tim speaks of.
UNfortunately the incline disappears into a huge rockfall that would need a jcb to dig out (or some mad bugger!)
I'm going to try to check the depth at the bottom of the incline and compare it with the new bottom of the mine.
RE driving levels horizontally...IF you think about it they could'nt drive them horizontally as they would be permanently underground!