London Underground is the world’s first underground railroad, which traffic was opened January 10, 1863. Its first line was built by the Metropolitan (translated as Capital). The company’s name was a perfect match for the new form of public transportation.
At that time the railroad had already gained recognition and carried passengers and cargo in many countries of the world, so the proposal of London lawyer Charles Pearson for the construction of an underground city railroad found enthusiastic supporters. The idea was realized in an unprecedentedly short period for those times – in less than four years. The first 6.5 kilometers of the line Pedington-Fedington Street was operated by steam traction, as the most advanced type of traction of the time.
The operation of the first subways was greatly complicated by high smoke levels, removing smoke from the tunnels was one of the most difficult problems. Separate sections tried to build open, and where it was impossible, ventilation hatches were equipped in large quantities.
But despite these inconveniences, the first subway showed great advantages over ground transport and began to develop quickly. Later, new companies were involved in subway construction, which led to some diversity of constructions and disconnection of lines. And only in 1933 the entire network of London Underground was transferred to the specially created Directorate of Urban Transport. This allowed to standardize the types of devices and constructions, to apply unified norms during the construction.
20 years later, by the end of 1953 new lines were laid to connect the disconnected sections. As a result, an inner ring was formed around the business districts of the City of London, called the Circle Line (Circle Line).
During 27 years the subway was operated by steam traction, and only on December 18, 1890 the underground line was switched to electric traction. The first electrified underground line connected central London to the South London Railway, and thus provided a reliable transport link between the business districts of the city center and the south of London.
Construction of the subway was carried out mainly by open method. The first segment built with closed method of work was constructed by engineer Berlow in 1870. Cylindrical bore shield with cast-iron tubing liner assembled with screw joints was used for tunnel boring. The tubes got their name from the word “tub” (tube). The cylindrical shape of the tunnel boring shields created at the time by engineer Greathead is still widely used today in various shield modifications for driving deep tunnels. In the late 40’s of our century in the construction of the subway also found widespread use of reinforced concrete tunnel tubes with bolted joints. It should be noted that the conditions of construction of the London Underground by deep-laid method are very favorable, as the ground is mostly clayey, waterproof, which does not require large waterproofing works.
Later on during the construction of Victoria radius with the length of 25 km (one of the first deep-laid tracks) the hinged-ring tunnel lining was applied. However this method was not widely used due to the insufficient stability of the construction as its reliability was ensured only by the supporting influence of the soil enveloping the tunnel. The most part of the stations of the London subway were constructed with the cast-iron tubing lining. Even now they are widely used during the construction of deep tunnels in the most difficult sections, as they have high reliability and create a strong structure.
During the construction of the London Underground the engineer Thomson designed a mechanical shield, which was first used on the Sengoral line. Later, engineer Price developed a modernized design of the mechanical shield, which with some modifications serves to the present day. The speed of shield tunneling with mechanical shields reaches 20-25 m per day.