How did they build the Tyne Tunnell?

Question

I went through it for the first time the other day and I was wondering how they built it?

Answer 1

The Tyne Tunnels between Howdon and Jarrow were first proposed by Durham and Northumberland County Councils in 1937 and approved by the minister of transport in 1943. The Tyne Tunnel Act, which approved the construction of three tunnels - a vehicular tunnel, cyclist tunnel and pedestrian tunnel - received Royal Assent in 1946. Work on the road tunnel did not commence until 1961 but the two smaller tunnels serviced by common escalators and lifts on both banks were started in 1947. The designers and engineers for the project were Mott, Hay and Anderson, the designers of the Tyne Bridge (1925 - 1928). The contractors were Charles Brand & Son. Construction began on 4th June 1947. Substantial difficulties with the stability of the strata were encountered when driving the tunnels, causing the north side to be built in compressed air. The work, as a result, took four years to complete. The tunnels were opened on 24th July 1951, the ceremony being performed by Alfred Barnes MP, Minister of Transport. 75% of the cost was met by the Ministry of Transport, the remaining quarter being split equally between Durham and Northumberland County Councils. The estimated cost of the works was £833,000, comprising £633,000 for the tunnels and £200,000 for the escalators. The overall proposed cost of the pedestrian, cyclist and road tunnels was originally estimated at £4 million.

Both pedestrian and cyclist tunnels are 900ft, (274.5m) in length, the pedestrian tunnel being 10ft. 6in (3.3m.) in diameter, the cyclists tunnel 12ft (3.7m). The tunnels lie at approximately 40ft (12.3m) below the river bed, approximately 85ft (25.8m) below High Water Level. The 200 ft (61m.) long single flight Waygood Otis escalators have a vertical rise of 85ft (25.8m.) On construction they were believed to be the longest single lift escalators in the world and are thought to be still the longest in this country. The escalators run at 150 ft (46 m.) per minute and are considered to be the first in the country built with the intention of carrying cyclists. A speed ray regulator, installed as part of the original design, controls the speed of the escalators depending on the level of usage, reducing the speed of travel when no one is using the escalators. The escalators are driven by worm gearing rotated by means of 80 h.p. electric motors. Originally the incoming electric supply consisting of 415 volts, three phase, alternating current was converted into direct current at the site. The escalators are still powered by the four original British Thomson-Houston Co. Ltd 80 BHP motors. Ventilation is provided by fans at each end of the tunnels which exhaust the air at mid point under the river and eject it up the lift shafts.