There are two principal methods of tunnel construction: the single-shell known as the Norwegian Method of Tunneling (NMT) and the double-shell referred to as the New Austrian Tunneling Method (NATM). Staunch supporters of both the methods consider their method to be the perfect one. Actually, nothing is perfect in this World and each method has its own merits and demerits. So, I invite the relevant experts to share their knowledge on the comparison of NMT and NATM, please
According to my knowledge, suggestions were given.
Please cross check it
1. Select New Austrian Tunneling Method for a wide range of geometry (shafts, junctions, non-circular tunnels andtunnels with variable shapes)
2. If you need expensive TBM equipment during excavation means go with New Austrian Tunneling Method to reduce cost
3. If the condition is softer ground & water table in highly permeable soils then Norwegian Method of Tunneling is preferred over New Austrian Tunneling Method.
Thanks Mr. Kabilan for starting a discussion on my question.
You are right that NATM can be used for tunnels with variable cross-sections and shapesand for shafts, junctions and adits while TBM can be sued for circular tunnles of uniform cross-section only.
However, the statement that " in case of soft ground with water bearing strata, NMT is prefered over NATM" may not be true. NATM is a very suitable method for soft ground. Actually the merits of NMT are as follows:
1. It is more economical due to single -shell lining
2. It takes a shorter time for completion.
3. it is preferred and hence has a wide spread use in poor countries in addition to the rich ones.
4. It is based on empirical analysis.
While the merits or advantages of NATM are as follows:
1. It is more safer due to double-shell lining.
2. It is preferred in rich countries
3. It has a wide spread publication record.
4. It is based on numerical/ analytical analysis.
You may add more merits of NMT and NATM.
Just a few points. NMT can never/has never been advised for soft water-bearing ground, unless the water could be solved with pre-injection. Shafi Ullah makes many good points. But do not assume NATM is safer. There have been too many problems with the temporary support phase of NATM, and numerous failures in this critical phase of tunnelling. Lattice girders are the softest form of support, because the reality is totally diferent from the drawings and models, where the actual effects of overbreak are 'always' ignored.
Dear Nick,
Some authors say that NATM is a tunnel construction method rather than a design one. Do you agree? And what about NMT? Is it a tunnel construction method or a tunnel design procedure?
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