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http://wikimapia.org/536639/Railway-Tunnel-Jamalpur This tunnel across the Rajmahal range was made between 1860-1861 and was the bottleneck in the faster proliferation of the East India Railway network, which started off from Howrah to Raneegunje(Raniganj, collieries near Asansol)[121 miles, 1855], reached Jamalpur (1862), reached Prayag 1862) and Delhi (1866) and finally Lahore (1866).

https://www.onepetro.org/conference-paper/ISRM-ARMS5-2008-087 Design Of A Railway Tunnel by R.K. Goel (Central Institute of Mining & Fuel Research), 2008 The existing Sahibganj Loop on the Kiul- Bhagalpur section of the East Central Railway crosses the Jamalpur hills through a tunnel between Jamalpur and Ratanpur Stations. The entire section has double broad gauge (BG) track but through the existing tunnel only single BG track is available. In order to have double track for operating up and down traffic on separate lines through the Jamalpur hills, another tunnel in the close proximity to existing tunnel is envisaged. The existing tunnel of the Ratanpur - Jamalpur section is 275m long aligned in East- West direction. The tunnel was constructed in 1861 and working satisfactorily since then [1]. No major problem and repair/maintenance works have been reported during the use of the tunnel. The D-shaped tunnel has arched roof of radius 3.963m. The height of the tunnel above the rail level is