Geological Survey of Norway (NGU)

Geology for society

Digging a tunnel starts from above

It is not that easy to build tunnels in Norway. History tells us there have been many problems with unstable rock masses and water leakage. Aerial surveys are the new way forward for identifying where the problem areas lie, and these surveys should be conducted before planning the construction of a tunnel.

Research shows that tunnel problems in Norway are often due to tropical weathering of bedrock that occurred when dinosaurs roamed the land.

A sketch depicting how tunnel problems vary with depth along the coast and surrounding areas. A single tunnel can have several types of problems if the height of the rock cover varies along the tunnel pathway. Illustration: NGU

Through geological and geophysical surveys, we know that deep weathering and clay, which are commonly found in coastal areas, can give headaches for the tunnel builders. From the great ancient rainforests warm, acidic water penetrated deep into existing bedrock fissures over millions of years. The process has been suitably called “deep weathering”.

The theory on deep-weathering zones suggests that tunnel problems will diminish with depth. Tunnel planners must take this fact into account when planning and estimating the cost of new tunnels. Today, in some terrain depressions, we can observe the remains of deep weathering.

Early in the 2000’s, NGU demonstrated that airborne magnetic surveys could have identified problem zones in the bedrock on sites located in Eastern Norway, long before the tunnel construction began.

The Norwegian company “Nye Veier” has recently decided to conduct bedrock mapping in southern Norway before choosing the final tunnel path.
They will save time and money.

Our products

No items found.
More products
No items found.
Hide products

Our articles

No items found.
More articles