4 ms·
It's easy to make a hole. Making a hole underground without making a hole aboveground is harder.
by iudqnolq 3y ago
It's easy to make a hole. Making a hole underground without making a hole aboveground is harder.
- hinkley 3y agoFor instance, the first subway systems in London were installed via cut and cover. Dig a trench, build a roof. Usually those trenches were in the street, or a former canal, not under a building. Using modern tunnel boring equipment, Seattle's attempt to move the downtown section of 99 into a tunnel ended up stalled for a year because the ground shifted and pinched the boring machine in place. Oopsie. And of course if you're worried about gasses, puncturing a solid piece of concrete is just going to make that problem worse.