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The historical Tunnel, which is accepted as the second underground metro in the world after the 1863 London Underground, was designed by the French engineer Eugene-Henri Gavand. The tunnel, which was built to provide transportation between Galata-Karaköy and Beyoğlu, two important centers of Istanbul, was commissioned on January 18, 1875. Tunnel celebrates its 148th anniversary this year

The symposium logo is formed by combining the Galata Tower, the "Tunnel," and the TBM.

Working Principle and Technical Properties of “Tunnel”

Figure 1. Tunnel Project (Gavand 1876)

The length of Tünel is 550.80 m, the width is 6.70 m, and the height is 4.90 m. The length of the railway inside is 626 m. It was first built as a double-track railway. The profile of the railway is not flat (Figure 1). There is a light ramp on the Karaköy side. The reason for this is that cars gain sufficient speed to overcome the next ramp. This image serves as a curved railway line. There is a 10-20 mm/m slope at the Karaköy side. This slope increases and reaches 149 mm/m. It remains constant until Tünel exit for 90 meters. Then, with a slight decrease in slope, it reaches Beyoğlu Station at 139 mm/m. The railway is 1.15 meters above sea level at Karaköy Station. The railway is 62.70 meters above sea level at Beyoğlu Station.

Figure 2- Sectional view of the tunnel (Gavand 1876)

There were two reasons to build the railway in a parabolic way. The first reason was to ensure a thick earth between Tünel’s upper level and the houses on the ground (Figure 5). Galata Tower’s location concerning the tunnel can be seen in this figure. On the other hand, the upper sectional view represents the Beyoğlu Station, and the lower sectional statements represent sections of the tunnel descending through sea level. Secondly, due to the high slope at Beyoğlu side, to ensure the cars pulled each other by the ropes to move without requiring the steam power entirely. Cars are hauled by a rope and driven by an engine located at one of the two terminals.

Figure 3- Longitudinal cross-sectional views of Tünel (Gavand 1876)

Figure 4 - Galata Tower & Tunnel Sectional

Reference: http://transport.itu.edu.tr/docs/librariesprovider99/belgeler/2014-03-14_tunnel_v9.pdf