Sunday, May 8, 2011

The Longest Railroad Tunnel in the World!

Port Townsend, today. This story "side tracked" by our celebration of the Grand Trunk Pacific anniversary last month. On March 23, 2011, AlpTransit Gotthard AG (ATG) announced the breakthrough of the West Tube of the Gotthard Base Tunnel.

A pair of Tunnel Boring Machines had completed the East Tube, last year, on October 15, 2010. This event completes the raw construction of the world's longest railroad tunnel, the twin tube Gotthard Base Tunnel, far beneath the Swiss Alps.

Actual tunnel boring began in 2003. The Gotthard Base Tunnel, at 57 km (35.4 miles), surpasses, by approximately 2 miles, the Seikan Tunnel in Japan. The Gotthard Base Tunnel is now the longest railroad tunnel in the world.

Moreover, track geometry will allow train speeds of freight 140 km/h (87 mph) and passenger 250 km/h (155 mph.)

The Gotthard Base Tunnel consists of two parallel single-track tubes, connected every 325m (1,066 feet) by 40m (131 foot) cross-passage. Overall, the tunnel system including the twin tubes, shafts and galleries, amounts to 151.8km (94 miles.)
  • Western tunnel: 56.978 km (35.404miles)
  • Eastern tunnel: 57.091 km (35.475miles)

The tunnels were excavated by four Herrenknecht AG Tunnel Boring Machines (TBM). Two sections, because of rock structure, were tunneled by conventional drill and blast.

The entire tunnel system will be waterproofed to prevent ground water from rusting re-bar in the concrete, and the railroad tracks. An "impermeable layer," composed of polyethylene sheeting and a hard plastic liner, separated by spacers. The impermeable layer will channel ground water around the tunnel to a drainage system, thereby protecting the main tunnel structure.

This diagram shows the various phases of construction as of May 1st. Work now focuses on tunnel lining, infrastructure systems, railway engineering (Positive Train Control) and installation of a $21 million ventilation system.

The tunnel will accommodate, in two separate tubes, more than 300 trains per day. Project plans allow two high-speed passenger trains and eight freight trains per hour, in each direction. Obviously, this requires a competent Positive Train Control system (PTC.)

Positive Train Control will be achieved through Electronic Interlocking, European Train Control System Level Two (ETCS-2) and a Centralized Traffic Control System (CTC.) PTC will permit travel speed to increase from 140 km/h (87 mph) to 250 km/h (155 mph) and transit time between Zurich and Milan will be reduced from 3 h 40 m to 2 h 40 m.

Of course, ventilation is a major concern. Track-side components have to withstand the pressure wave created by a high speed train in transit. And one cannot dismiss the likelihood of fire. A touchy subject for sure.

However, the facts are, long tunnels have a deadly record. You may recall the near catastrophic fires in the "Chunnel Fire" in 1996 and 2008. The fire in 1996 caused $70 million worth of damage.

The Gotthard Base Tunnel will look very similar to the 34.57 km (21.5 mile) Lötschberg Base Tunnel, also in Switzerland, commissioned in 2007.

Factoid: In those areas where the Tunnel Boring Machines could not be used because of rock conditions, dynamiting was employed. The raw tunnel diameter was increased by three feet. Squeezed by millions of tons of rock from the Alps, the tunnel compressed to project diameter!

Factoid: 400,000 concrete ties (sleepers) will be installed.

AlpTransit Gotthard is expected to "hand over the keys" to Swiss Federal Railways (SBB,) in operating condition, in May 2016.

Further readings:

Building the Gotthard Base Tunnel The page is in German, but there is a button in the top right page corner, to select the English version.

Gotthard Base Tunnel
: Describes the hazards of construction of a multifunctional station in a Large Fault Zone

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