The Channel Tunnel (known as Tunnel sous la Manche in France) — “The Chunnel” — is a 50.46km (31.35 mi) railway tunnel that connects Folkestone (Kent, England, UK) with Coquelles (Hauts-de-France, France) beneath the English Channel at the Strait of Dover. It is the only fixed link between the island of Great Britain and the European mainland. At its lowest point, the Channel Tunnel is 75m (250 ft) deep below the sea bed and 115m (380 ft) below sea level. At 37.9km (23.5 mi) in length, it has the longest underwater section of any tunnel in the world and is the third-longest railway tunnel in the world. The Chunnel is comprised of three separate tunnels that run parallel to one another: One train tunnel that runs south (United Kingdom to France), one train tunnel that runs north (France to United Kingdom), and one service tunnel. The tunnel carries high-speed Eurostar passenger trains, the Eurotunnel Shuttle for road vehicles and international freight trains. It connects end-to-end with the high-speed railway lines of the LGV Nord in France and High Speed 1 in England.

In 2017, the tunnel’s rail services carried 10.3 million passengers and 1.22 million tonnes of freight, and the Shuttle carried 10.4 million passengers, 2.6 million cars, 51,000 coaches, and 1.6 million lorries (equivalent to 21.3 million tonnes of freight), as compared with 11.7 million passengers, 2.6 million lorries and 2.2 million cars by sea through the Port of Dover. The privately financed tunnel, which ultimately cost $14.7 billion, has enabled 500 undersea train trips a day at speeds reaching nearly 100 mph (160 kph).

Planning the Chunnel

The idea of connecting the UK and France by tunnel is much older than people think – dating back to the early 1800s when its supporters included Napoleon Bonaparte. At the time, pressure over the compromising of national security disrupted attempts to build one.

Work on experimental tunnels started back in 1880 at Abbot’s Cliff near Folkestone. Many of the workers used hand tools, but a state-of-the-art boring machine was also used. Work was eventually abandoned until construction on the tunnel as we now know it began again in the late 1980s.

The idea of constructing a tunnel under the English Channel was revived in 1986. A rail tunnel was chosen over proposals for a very long suspension bridge, a bridge-and-tunnel link or a combined rail-and-road link. Digging began on both sides of the Strait of Dover in 1987 and was completed in 1991.

By 1990, when it became clear that the project was at risk. Bechtel, which has offices in Texas, Virginia, England, and Chile, was called in to get the project back on track. Bechtel helped manage the project to its successful completion in 1994, providing management, technical, and construction expertise, which helped restore the trust of investors and financial institutions. Bechtel’s project team used 11 giant, laser-guided tunnel-boring machines to dig some 48 mi (77 km) of the tunnel — a world record.

The Channel Tunnel’s Construction

The digging of the Chunnel began simultaneously from the British and the French coasts, with the finished tunnel meeting in the middle. Digging was done by huge tunnel boring machines, known as TBMs, which cut through the chalk, collected the debris, and transported the debris behind it using conveyor belts. As the TBMs bore through the chalk, the sides of the newly dug tunnel had to be lined with concrete to help the tunnel withstand the intense pressure from above and to help waterproof it.

One of the most difficult tasks was making sure that the British and French sides of the tunnel actually lined up in the middle. Special lasers and surveying equipment were used; however, with such a large project, no one could be sure it would actually work. Since the service tunnel was the first to be dug, it was the joining of the two sides of this tunnel that caused the most fanfare. On December 1, 1990, the meeting of the two sides was officially celebrated when two workers—one British and one French—were chosen by lottery to be the first to shake hands through the opening.

Although the meeting of the two sides of the service tunnel was a cause of great celebration, it wasn’t the end of the project. Both the British and the French kept digging. The two sides met in the northern running tunnel on May 22, 1991, and then, only a month later, they again met in the middle of the southern running tunnel.

But even those events weren’t the end of the construction. Crossover tunnels, land tunnels from the coast to the terminals, piston relief ducts, electrical systems, fireproof doors, ventilation system, and train tracks all had to be added. Also, large train terminals had to be built at Folkestone and Coquelles.

On December 10, 1993, the first test run was completed through the entire Chunnel. After additional fine-tuning, the tunnel officially opened on May 6, 1994. It was estimated to cost £5.5 billion in 1985 (about $6.2 billion USD, 1985 prices) and was, at the time, the most expensive construction project ever proposed. The final cost totaled £9.5 billion by the end of its construction (about $14.5 billion USD in 1994) — well over its predicted budget. The cost overage was due to delays related to construction cost, equipment delivery, and testing problems, as well as changes to the design of the project during construction to increase safety.

In 2007, the Channel Tunnel Rail Link (CTRL), also called High Speed 1, was opened to connect the Chunnel with London, facilitating the even greater movement of international passenger traffic between mainland Europe and the UK. The high-speed railway runs 108 km (67 miles) and crosses under the Thames River. Its trains can reach speeds of up to 300 km (186 miles) per hour.

Traveling through the Chunnel

Foot passengers can travel with Eurostar between UK stations (London St Pancras International, Ebbsfleet International in north Kent, or Ashford International in south Kent) and stations on the continent. People who want to travel in their own vehicle or on a coach can use the Eurotunnel Le Shuttle between Folkestone and Calais. Before traveling through the tunnel with either Eurostar or Eurotunnel, travelers must go through security, border, and ticket checks.

Eurotunnel Shuttles, Eurostar, and freight trains run on two monodirectional single-track tunnels. They are connected every 375m by cross-passages to a service tunnel, a road tunnel for maintenance operations, and the evacuation of passengers in the event of a fire or other calamity. Two undersea crossovers were also included in the design, bringing flexibility to operations, as trains can pass from one railway tunnel to the other, in particular during nightly maintenance periods. In normal operations, Eurotunnel Shuttles use the south tunnel in the France–UK direction and the north tunnel when traveling in the UK–France direction.

The two rail tunnels are 7.6m in diameter and 30m apart. Each rail tunnel has a single track, overhead power line (catenary), and two walkways (one for maintenance purposes and the other on the side nearest the service tunnel for use in the event of an emergency evacuation). The walkways are also designed to maintain a shuttle upright and in a straight line of travel in the unlikely event of a derailment.

The service tunnel is 4.8m in diameter and lies between the two rail tunnels 15m away from each of them. The service tunnel allows access to maintenance and emergency rescue teams and permits the evacuation of passengers in the event of an incident. It also serves as access to the ventilation of the entire infrastructure. For optimum safety, it is kept in a state of air overpressure and remains safe from fumes in case of fire in one of the railway tunnels.

Have you had any experience visiting or working with the Chunnel? Let us know your thoughts below.