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Originally posted by Phage
Yes. But you're talking about underground tunnels.
If you dig the tunnels above ground...
Time for bed.
Originally posted by gariac
There are numerous threads about secret underground tunnels on ATS. As luck would have it, they are building a new bore in the Caldecot tunnel (San Francisco bay area route 24). Let's look at the facts. The new bore is 3389ft in length. The tunnel portion of the project will take at least 3 years with two bore machines approaching from both ends. Cost is $420 million. Remember, this is 3 years for far less for a mile.
The point is look at how long it takes to build a tunnel IN THE OPEN. Imagine if you have to tunnel in secret. Noise and off-haul is hard to hide.
This tunnel is in a mountain, which makes the job easier since the mountain earth is more stable than what you find underground.
The moon may be a harsh mistress, but lately she has been giving up her secrets. Scientists have spotted a deep hole in the lunar surface that goes at least 260 feet down and is believed to open into an underground tunnel more than 1,200 feet wide. The discovery is powerful evidence for long, winding tunnels carved by lava beneath the lunar surface. Such tunnels, whose existence has long been hypothesized, could provide shelter for future astronauts or colonists against the harsh radiation and surface temperatures on the moon. Previous signs of such tunnels only existed as surface features called rilles, which hinted at hollow lava tubes below. Researchers only found the hole by poring through images taken by Japan's deceased Kaguya lunar probe.