Next Big Thing From Elon Musk? It Could Be 'Boring' (usatoday.com)
A string of tweets put out by serial tech entrepreneur Elon Musk on Saturday hints that his entrepreneurial future may be a little "boring." USA Today reports: The Tesla and SpaceX founder got on Twitter on Saturday morning to rant about an issue he seems to find irksome -- traffic. Musk has also been working on resolving his frustration with traffic issues through above-ground means with his Hyperloop venture, which proposes a plan for mass-transit pods moving through above-ground tubes. But that doesn't appear to be enough, commenting: "Traffic is driving me nuts. Am going to build a tunnel boring machine and just start digging..." He even offered up a name for the venture, calling it "The Boring Company," and began branding it with a slogan: "Boring, it's what we do." Then capped it off by tweeting, "I am actually going to do this."
Regardless of how deep, it will also have to be fast. I believe current borers (correct term?) drill at the rate of 1-2 metres per day.
According to Crossrail, the largest distance tunnelled by one of their boring machines in a single day was "72 metres by Ellie on 16 April 2014 between Pudding Mill Lane and Stepney Green". So 1-2 metres seems to be out by quite a bit.
Southern California isn't the best place for a subway. There are currently only two underground subway lines, and they came in vastly over budget - the Metro Red line's original cost estimate was $400 million; it was completed for $4.5 billion. It held the record for the most expensive civic construction project until Boston's Big Dig.
The reason is that SoCal is full of oil. If you visit, you'll see functioning oil pumps scattered around in random places. It bubbles out of the ground naturally in the La Brea Tar Pits, and into the surrounding ocean as underwater oil seeps. When they dug the first tunnels for the Red line, the workers returned the next day to find oil and tar seeping in through the walls of the freshly-dug tunnel. They had to stop construction until they could come up with new ways to hold back the seepage and insure it wouldn't become a problem in the future decades of subway operation. (The Big Dig was expensive because of similar problems, except with seawater seepage.)
Oh yeah, the earthquakes tend to be a problem too. Especially if your tunnel crosses over a fault line.