Tunnels and underground excavations - Tunneling techniques ...- Tunnelanlage in Bangalore sanieren ,Tunnels and underground excavations - Tunnels and underground excavations - Tunneling techniques: Tunnels are generally grouped in four broad categories, depending on the material through which they pass: soft ground, consisting of soil and very weak rock; hard rock; soft rock, such as shale, chalk, and friable sandstone; and subaqueous. While these four broad types of ground condition require ...Out of ideas on ground, govt plans four tunnels to ease ...As all overground solutions to tackle traffic congestion have run into trouble, the government seems to be looking beneath for solutions.