Wayne Holt, Executive Director at leading Specialist Structural and Civil Engineering practice Design2e, examines Boris Johnson’s dream of a Channel bridge…
It was with much interest that I read Boris Johnson’s unscheduled comments about building a bridge over the English Channel.
The UK Foreign Secretary apparently ran the idea of a 22-mile bridge past French President Emmanuel Macron at a meeting last week.
Judging by subsequent comments from Downing Street distancing themselves from the proposal, I’m not convinced the project was an agenda item. It seems like Mr Johnson was going a bit off-piste. Either way, it’s certainly caught the attention of the national media.
There has been much discussion but, from an engineering point of view at least, it is entirely feasible. A huge financial undertaking, but feasible.
In places such as China, Japan and Taiwan, longer bridges exist than would be required to join us with our Gallic neighbours, though officially the longest bridge over continuous water is Lake Pontchartrain Causeway in Louisiana, USA, which measures 23.79 miles. The structural technology is well proven.
There are potential problems as The English Channel is the world’s busiest shipping lane, but there are always possible solutions. As mooted by others in the industry, one option could be building two islands with the road passing through a tunnel between them. That way, you retain a stretch of water through which the ships can pass unhindered.
Perhaps the most curious question is which side of the road would the cars drive on, given the driving laws in each country. But even this issue has been resolved elsewhere, with an ingenious “flipper” bridge being used between Hong Kong and mainland China.
The flipper bridge sees one side of the road dip under the other, funnelling cars that were traveling on the left to the right and vice versa. This is innovative engineering at its best – finding effective solutions to complex problems.
If the Channel bridge ever did materialise, it’d certainly be a magnificent structure which would symbolise the strong bond between two traditional European superpowers. It could even enable the mid-Channel islands to become tourist attractions in their own right with hotels, restaurants and other attractions.
This is certainly not the first time a Channel bridge has been suggested. In fact, the Victorians were considering it in 1893!
They proposed a 21-mile long bridge, consisting of 73 piers, with spans arranged alternately in distances of 1,312ft (nearly 400m) and 1,640ft.
All but one would’ve been in the sea, with the deepest founded at 167ft and the masonry carried 46ft above the highest tides. The estimated cost was around £38.4m (£2.3bn at today’s prices).
They believed the technical challenges involved were far from insurmountable — and argued that the work carried out on the Forth and Brooklyn Bridges was evidence that the Channel bridge was a feasible proposition.
Their solution to the shipping issues? An elaborate system of illumination signals and foghorns.
The idea then reared its head again prior to the construction of the Channel Tunnel, which opened in 1994. A submission for a £3bn, three-lane motorway link was made to transport officials in 1981, but it was considered unrealistic at the time.
So the burning question is, will we ever be able to drive from our shores into France? From an engineering point of view at least, it’s certainly possible. For now, it’s just heart-warming to hear people talk about structural engineering with such passion.