"Concrete can tolerate much more force that previously believed, which could open the door to a new kind of road structure: a floating tunnel.
The E39 is a nearly 1100-km long coastal road that crosses seven major fjords by use of ferries. Norwegian authorities are working to improve the road by eliminating ferry crossings, which in addition to being costly, mean that drivers have to wait for ferries if they don’t arrive at the crossing at exactly the right time.
The biggest hurdle to this improved coastal road is found at Sognefjord, Norway’s longest and deepest fjord. At its mouth, the fjord is 2.3 miles wide and 4300 feet deep. Building a conventional suspension bridge would require a structure that would be double the length of the existing record holder and would be three times the length of the Golden Gate Bridge in San Francisco. To hold the suspension bridge, the two towers at either end would have to be 1500 feet high, or 500 feet taller than the Eiffel Tower.
But a series of experiments from the Norwegian University of Science and Technology’s (NTNU) Centre for Advanced Structural Analysis, or CASA, could pave the way for an entirely new type of water crossing: submerged floating tunnels. Experiments in a shock tube at CASA’s research laboratories show that concrete can tolerate much more pressure than previously thought."
https://maritime-executive.com/blog/shock-testing-paves-the-way-for-floating-tunnels
The E39 is a nearly 1100-km long coastal road that crosses seven major fjords by use of ferries. Norwegian authorities are working to improve the road by eliminating ferry crossings, which in addition to being costly, mean that drivers have to wait for ferries if they don’t arrive at the crossing at exactly the right time.
The biggest hurdle to this improved coastal road is found at Sognefjord, Norway’s longest and deepest fjord. At its mouth, the fjord is 2.3 miles wide and 4300 feet deep. Building a conventional suspension bridge would require a structure that would be double the length of the existing record holder and would be three times the length of the Golden Gate Bridge in San Francisco. To hold the suspension bridge, the two towers at either end would have to be 1500 feet high, or 500 feet taller than the Eiffel Tower.
But a series of experiments from the Norwegian University of Science and Technology’s (NTNU) Centre for Advanced Structural Analysis, or CASA, could pave the way for an entirely new type of water crossing: submerged floating tunnels. Experiments in a shock tube at CASA’s research laboratories show that concrete can tolerate much more pressure than previously thought."
https://maritime-executive.com/blog/shock-testing-paves-the-way-for-floating-tunnels