TUNNELING MACHINES IN SOFT GROUND - A COMPARISON OF SLURRY AND EPB SHIELD SYSTEMS

Thanks to advances in tunnelling machine technology, tunnels can be driven by machines even in very difficult ground conditions. The two most important objectives in machine tunnelling are: (1) to support the ground reliably during excavation; and (2) to hold the surrounding ground behind the shield tail in balance by grouting while the lining is being erected. The author compares two established machine tunnelling methods-the slurry shield and the earth-pressure balanced shield tunnelling system-with regard to how they achieve these two objectives.