Tunnel
boring machines are those machines that are used for excavating tunnels
of circular cross section of different diameters. Through tunnel boring
machines (TBM), tunnels are excavated in different types of geologies. It is
alternate to blasting and drilling, which without disturbing the
surroundings produces a smooth tunnel wall. Tunnel boring machines (TBM)
generally has protective shield for the tunneling purpose. The machines
consists of either single shield or double shield depending upon the
nature of the topography. Various types of tunnel boring machines that
are used for the purpose of excavation are :
