Tunneling Works

Pamco Engineering performs tunneling works using the New Austrian Tunneling Method (NATM). This traditional tunneling method is based on staged progress according to soil conditions while installing primary support comprised of a combination of bolting and shotcrete. Final support is provided by various methods using shotcrete or form-cast concrete. This excavation method, applied in soft soils, is executed in stages beginning at the crown of the tunnel in stepped progression (benching down) to the bottom (invert) of the tunnel. The number of steps is related closely to soil type and strength. NATM can also be applied in rock. When rock conditions are suitable, tunneling can also progress by controlled blasting.

When applying the NATM method, the tunnel cross-section takes on an oval-like geometric shape. In soil or rock conditions that require more massive primary support, tunneling progresses in small steps with the installation of lattice girders to the extent necessary, ceiling bolting, the use of forepoling umbrella tubes and shotcrete applied in 10-15 cm thick layers on steel fabric reinforcing. This may be termed an “observational method” since advancement of tunneling is accompanied by monitoring of soil displacements, both in the tunnel cross-section itself and on the surface as well as at depth above the tunnel ceiling. Continuous monitoring of the soil, the installation of lattice girders and bolting allows real-time decisions to be made about the span of the excavated step, the nature of support and its density. The NATM method is clearly based on decisions taken by the “man on the scene” and is combined with continual geological tracking.

Pamco Engineering has all equipment necessary for installing preliminary support, a shotcrete robot, bolting machines and forepoling umbrella machines. We employ skilled crews who are capable of providing solutions in real-time in all soil or rock conditions.

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