Norwegian Tunnelling Network (NTN)
The NTN cluster of 25 leading companies and institutions in the Norwegian tunneling sector have joined forces to be able to offer products, equipment, knowledge and services to international tunneling and mining. The group consists of various product and equipment manufacturers, consultants, contractors (including special techniques providers) as well as the largest public sector tunnel Owner and academic and research institutions.
Norwegian tunneling is correctly known to be cost and time efficient, but there is also the general and false impression abroad that this positive situation is primarily linked to mostly “excellent” ground conditions. There is a sliver of truth in this assumption, but even in Norwegian hard rock environment, occurrence of extremely poor ground is normal. The volcanic rocks in the Oslo field that are mixed with sedimentary rocks, typically offer demanding conditions and our high mountains often cause extreme rock bursting and large deformations. Sub-sea road tunnels down to almost 300 m below sea level and tunnels on land with recorded static water head above 80 bar, sometimes with extreme water ingress have been successfully executed. By considering these highly variable conditions and by far the highest tunneling volume anywhere in the world (per capita), it becomes obvious that the favourable cost and short construction time results have been achieved in spite of ground conditions, not because of them.
Supporting the construction efficiency are the normal risk sharing contract forms, modern equipment, advanced and safe temporary and permanent lining solutions utilizing permanent rock bolts and sprayed concrete with fibre reinforcement, probe drilling, ground water control and stability improvement by pre-excavation grouting, ample availability of experienced miners, contractors, engineers and consultants. The “Norwegian Way of Working” (NWW) is characterized by a small and efficient Site administration and only strictly necessary bureaucracy, while still maintaining full production control without compromising safety or quality. With trained professionals at all levels during project construction, any necessary adaptations to extreme conditions can be quickly decided and implemented with not more than required delay to progress.
It is appreciated that not all of the above mentioned elements of cost and time efficient tunneling will be readily available or even applicable everywhere. However, through NTN and its members, products, equipment, knowledge and services can be accessed as needed and can be implemented as far as locally possible to provide benefits to projects anywhere. By contacting NTN and describing any local project problem or wish-list for improved efficiency and lower cost, NTN can work through its members to identify the most useful contacts for development of better solutions.
If your projects are located in hard rock in mountainous and highly variable ground, if you are frequently facing squeezing ground, rock bursting and major water inrush and you need to reduce risk by adopting a maximum flexibility and adaptability excavation method, then you should in many cases look at a drill and blast solution. This kind of tunnelling represents the primary strength of NWW, regardless of what the purpose of the tunnel may be. Norwegian tunneling was also a pioneer in hard rock excavation by TBMs starting more than 40 years ago and as reflected by the sophisticated (cutter) cost and time prognosis model developed by NTNU, now being used world wide.