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.
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.