Natm New Austrian Tunneling Method (natm)

This is the most common method. It originates in hard rock tunneling and utilizes rockbolts and shotcrete applied immediately after blasting. This is often followed by a cast in-situ concrete lining using formwork.

The New Austrian Tunneling Method (NATM) was a methodical approach to tunneling developed in Austria between 1957 to 1965 by Ladislaus von Rabcewicz, Leopold Muller, and Franz Pacher. The over-arching idea behind NATM is to use the geological stress of surrounding rock mass to provide stabilization and support to the tunnel itself.

According to the Rabeciwz, the principal founder of NATM, the method can be explained as “a new method consisting of a thin sprayed concrete lining, closed at the earliest possible moment by an invert to a complete ring – called an “auxiliary arch” – the deformation of which is measured as a function of time until equilibrium is obtained.”

The three key points Rabcewizc stressed were the application of thin-sprayed concrete lining known as shotcrete, closure of the ring as soon as possible, and the systematic deformation measurement.

As a Construction Method NATM includes such features as:

- The tunnel is sequentially excavated and supported, and the excavation sequences can be varied.

- The initial ground support is provided by shotcrete in combination with fiber or welded-wire fabric reinforcement, steel arches, lattice girders, and sometimes ground reinforcement.

- The permanent support is usually a cast-in-place concrete lining.

2.13. Translate the following text in written form with a dictionary. Try to manage within 15 minutes. Tunnel Boring Machine (tbm) method

A tunnel boring machine (TBM) also known as a “mole”, is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through hard rock, sand, and almost anything in between. Tunnel diameters can range from a metre (done with micro-TBMs) to almost 16 metres to date. Tunnels of less than a metre or so in diameter are typically done using trenchless construction methods or horizontal directional drilling rather than TBMs.

Tunnel boring machines are used as an alternative to drilling and blasting (D&B) methods in rock and conventional “hand mining” in soil. TBMs have the advantages of limiting the disturbance to the surrounding ground and producing a smooth (гладкий, ровный) tunnel wall. This significantly reduces the cost of lining the tunnel, and makes them suitable to use in heavily urbanized areas. The major disadvantage is high cost. TBMs are expensive to construct, and can be difficult to transport. However, as modern tunnels become longer, the cost of tunnel boring machines versus (в сравнении с)drill and blast is actually less – this is because tunnelling with TBMs is much more efficient and results in a shorter project.

The largest diameter TBM, at 15.43 m, was built by Herrenknecht AG for a recent project in Shanghai, China. The machine was built to bore through soft ground including sand and clay. The largest diameter hard rock TBM, at 14.4 m, was manufactured by The Robbins Company for Canada’s Niagara Tunnel Project. The machine is currently boring a hydroelectric tunnel beneath Niagara Falls.