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If you were to assume the soil you are excavating is very forgiving and your street is wide enough, you might be able to dig a trench that is 10 meters wide and 30 meters deep (you cannot dig straight down or the walls might cave in, unless you plan on using shotcrete, which you may or may not have to remove when you start backfilling the area). Now, we are talking about removing 975 cubic meters per meter of trench, if your street is 100 meters long, that is 97500 cubic meters you will need to excavate, at a rate of 33.1 cubic meters per hour, you would need to work around the clock for more than 122 days in order to excavate the trench. You also have to take into account that you will need a place to store the 97500 cubic meters of soil you just excavated, which now have swollen up to 126800 cubic meters, the average dump truck can hold around 10 cubic meters, it would take you more than 10000 trips to move the soil. This is just one street, never mind the fact that in order for this to be useful you will need to have at least a few kilometers of tunnel at a time. Also, even if there are no internal combustion engines running in the tunnel, you still need ventilation shafts, subterranean metros have them for a myriad of reasons, even though there are no dinosaur squeezings being burned in the tunnels, for example, what happens if one of those very powerful batteries that run your Tesla happen to catch fire? People might suffocate if you can't force air into the tunnel. Its a nice idea, but there is a reason why tunnel boring machines and vertical shaft sinking machines are so widely used on built-up areas. |