It won't work.
The reason it won't work is that the tube has to be 1) straight (so that a capsule can move through it safely at 700 miles per hour) 2) sealed (so that a partial vacuum can be maintained) and 3) hundreds of miles long (so that you can travel useful distances). A tube that is is straight, sealed, and hundreds of miles long will undergo thermal expansion that will amount to hundreds of feet of movement at either end. Until and unless this problem is solved, the hyperloop won't fly. (This is far from the only show-stopper, but it's the easiest one to explain.)