Tunneling in Soils

Tunneling In Soils

The construction of tunnels in soils has traditionally been a challenging task as these excavations must be swiftly supported. Moreover, the face of the excavation is usually also supported to prevent failure. When using the conventional tunneling method (typically referred to as New Austrian Tunneling Method, NATM), blasting is not preferred and the excavation is typically conducted by mechanical means, in multiple phases. The tunnel’s section is excavated in several phases to ensure its stability.

When the mechanized method is selected, TBM machines utilize a shield to apply pressure at the tunnel’s face to prevent instability and control high groundwater pressures. These TBMs are known as EPBMs (Earth Pressure Balance Machines). An EPBM uses an advanced system that applies pressure against the excavated front utilizing the excavated material (muck) to balance the total earth pressures. Special additives are used to correct the consistency of the excavated material in order to turn it into a transportable and impermeable soil paste.