Author Topic: Why are Tunnels Round?  (Read 22304 times)

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Offline Ben Valmores

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Re: Why are Tunnels Round?
« Reply #75 on: March 27, 2013, 12:03:58 PM »
and...another...
“Destiny is not a matter of chance. It is a matter of choice: It is not a thing to be waited for, it is a thing to be achieved.”
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Offline Ben Valmores

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Re: Why are Tunnels Round?
« Reply #76 on: March 27, 2013, 12:07:14 PM »
and more...
“Destiny is not a matter of chance. It is a matter of choice: It is not a thing to be waited for, it is a thing to be achieved.”
---William Jennings Bryan

Offline Ben Valmores

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Re: Why are Tunnels Round?
« Reply #77 on: March 27, 2013, 12:11:10 PM »
another sets..

THESE PHOTOS ARE NOR MINE....CREDITS TO THE BLOGGER,,,,ONSENFEEL JAPAN
“Destiny is not a matter of chance. It is a matter of choice: It is not a thing to be waited for, it is a thing to be achieved.”
---William Jennings Bryan

Offline Ben Valmores

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Re: Why are Tunnels Round?
« Reply #78 on: March 27, 2013, 12:14:01 PM »
last...
“Destiny is not a matter of chance. It is a matter of choice: It is not a thing to be waited for, it is a thing to be achieved.”
---William Jennings Bryan

Offline ZOBEX

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Re: Why are Tunnels Round?
« Reply #79 on: March 27, 2013, 03:24:40 PM »
is it true that blasting the entrance of a tunnel locked in pressure to keep the sides intact, and once closed tunnel is opened, in a few days, it begins to collapse?
No you don't have to blast the entrance. just in our site here, we encounter a closed tunnel, in the entrance we found a diagram stone which is the same form with the tunnel. the openings are in both sides and at the back. But the our operation was stopped due to our diggers having nightmares. they said that there's a tall man wants to kill them. two of my diggers almost the same story about their nightmares.
Atan, read the post of Kaloy again. What he was saying, when the Japanese Sealed off the Tunnel by Blasting the entrance, the pressure resulting from the Blast was sealed inside the tunnel when the tunnel entrance  collapsed and thereby sealing the entrance. When the tunnel was opened, the tunnel, he says, begins to collapse after a few days because he thinks the pressure inside the tunnel was released after the entrance was opened. My answer was NO as the tunnel is normally earthen material and earth is porous, meaning it will not stop or seal in Water nor Air. Hopefully my explanation clarified the matter.

Not exactly.  As a Structural Geologist, there is a couple of factors involved.  A tunnel that has remained open from the start has a natural rhythmic exchange of air with the outside.  This includes, moisture and barometric pressure.  A closed tunnel has a predominately flat line moisture and barometric pressure changes are modulated to very long periods.  On the micro level, moisture creep (that means changes up and down in percentage saturation) will make the soil or rock expand and contract, this is exaggerated with barometric pressure changes such as weather fronts passing by.  A sealed tunnel gets stabilized to the very small changes due to it's isolation.  Once the tunnel is opened up to the outside atmosphere, the tunnel walls start to creep.  This is when the surfaces start to exfoliate, that meas flake off in spots up to extensive failure as in a roof collapse.  It is a well known fact to miners and geologists that once opening a formerly sealed old tunnel, the tunnel will start to destabilize in about 3 weeks, that is about 21 days.  This is an approximate.  We have always had a rule, once a tunnel is opened up, the freaking thing will start falling apart in about 3 weeks.  So get in and get out fast.  The longer you wait, the greater a chance for a collapse and getting caught inside alive.  I have opened several sealed tunnels in the islands and the results are always the same.  Another factor that can be a problem is developing water intrusion.  A sealed pressure tunnel may resist water intrusion.  Once the tunnel starts to breath, water intrusion may very well develop and steadily increase.  Been there and done that unfortunately.

Z


Offline Gboy

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Re: Why are Tunnels Round?
« Reply #80 on: March 27, 2013, 04:30:59 PM »

Another Japs tunnel inside a granite mountain.....whew  :o ...just chiseling a small portion of the granite rocks is difficult enough, just imagine you tunnel 100 meters long....waaaaa  ;D

And whats the purposes of those protruding train railings and rebars anyway?..ask the Japanese who put it there  ;D

Offline zeeker

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Re: Why are Tunnels Round?
« Reply #81 on: March 27, 2013, 09:16:22 PM »
is it true that blasting the entrance of a tunnel locked in pressure to keep the sides intact, and once closed tunnel is opened, in a few days, it begins to collapse?
No you don't have to blast the entrance. just in our site here, we encounter a closed tunnel, in the entrance we found a diagram stone which is the same form with the tunnel. the openings are in both sides and at the back. But the our operation was stopped due to our diggers having nightmares. they said that there's a tall man wants to kill them. two of my diggers almost the same story about their nightmares.
Atan, read the post of Kaloy again. What he was saying, when the Japanese Sealed off the Tunnel by Blasting the entrance, the pressure resulting from the Blast was sealed inside the tunnel when the tunnel entrance  collapsed and thereby sealing the entrance. When the tunnel was opened, the tunnel, he says, begins to collapse after a few days because he thinks the pressure inside the tunnel was released after the entrance was opened. My answer was NO as the tunnel is normally earthen material and earth is porous, meaning it will not stop or seal in Water nor Air. Hopefully my explanation clarified the matter.

Not exactly.  As a Structural Geologist, there is a couple of factors involved.  A tunnel that has remained open from the start has a natural rhythmic exchange of air with the outside.  This includes, moisture and barometric pressure.  A closed tunnel has a predominately flat line moisture and barometric pressure changes are modulated to very long periods.  On the micro level, moisture creep (that means changes up and down in percentage saturation) will make the soil or rock expand and contract, this is exaggerated with barometric pressure changes such as weather fronts passing by.  A sealed tunnel gets stabilized to the very small changes due to it's isolation.  Once the tunnel is opened up to the outside atmosphere, the tunnel walls start to creep.  This is when the surfaces start to exfoliate, that meas flake off in spots up to extensive failure as in a roof collapse.  It is a well known fact to miners and geologists that once opening a formerly sealed old tunnel, the tunnel will start to destabilize in about 3 weeks, that is about 21 days.  This is an approximate.  We have always had a rule, once a tunnel is opened up, the freaking thing will start falling apart in about 3 weeks.  So get in and get out fast.  The longer you wait, the greater a chance for a collapse and getting caught inside alive.  I have opened several sealed tunnels in the islands and the results are always the same.  Another factor that can be a problem is developing water intrusion.  A sealed pressure tunnel may resist water intrusion.  Once the tunnel starts to breath, water intrusion may very well develop and steadily increase.  Been there and done that unfortunately.

Z

does this holds true even if the quality of soil inside the tunnel is strongly bonded? (just like the pictures above posted by sir ben)
continue the journey

Offline KIZUNA

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Re: Why are Tunnels Round?
« Reply #82 on: May 15, 2013, 10:34:24 PM »
TUNNEL WARFARE
Light travels faster than sound. This is why some people appear bright until you hear them speak.

KZN

Offline KIZUNA

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Re: Why are Tunnels Round?
« Reply #83 on: May 15, 2013, 11:25:10 PM »
An excerpt from a book....

Example of an IJA underground defense system drawn from a memory from a Japanese Prisoner of War and later diagrammed by Postwar Japanese Investigators.
The network was dug more than 32 feet deep, with 17 entrances along its 540 yards lenght and sheltered 300 men. All of the defenders died in battle others committed suicide except for the private who drew the map; he was captured unconscious after he had shot himself
Light travels faster than sound. This is why some people appear bright until you hear them speak.

KZN