Manual Shield Tunnelling
In early shield tunnelling, the shield functioned as a way to protect labourers who performed the digging, and moved the shield forward, progressively replacing it with pre-built sections of tunnel wall. The early deep tunnels for the London Underground were built in this way. The shield divided the workface into overlapping portions that each worker could excavate.
Read more about this topic: Tunnelling Shield
Famous quotes containing the words manual and/or shield:
“Criticism is infested with the cant of materialism, which assumes that manual skill and activity is the first merit of all men, and disparages such as say and do not, overlooking the fact, that some men, namely, poets, are natural sayers, sent into the world to the end of expression, and confounds them with those whose province is action, but who quit to imitate the sayers.”
—Ralph Waldo Emerson (1803–1882)
“Vice is its own reward. It is virtue which, if it is to be marketed with consumer appeal, must carry Green Shield stamps.”
—Quentin Crisp (b. 1908)