More than a few tunnels were converted to open cuts after earthquake-induced collapse, since the ground was too unstable to re-tunnel and loose enough to be readily removable with modern earthmoving equipment.
A lot of very early tunnels, dug with hand tools, wheelbarrows and black powder, were made just barely large enough to clear the locomotives and rolling stock of the day. If the same track was built today, using present day explosive techniques, power shovels and haul trucks, many of those tunnels would have been open cuts from the beginning.
One of the major considerations about daylighting a tunnel is the nature of the covering material and the shape of the ground. The former NYC tunnels on the east bank of the Hudson River above Poughkeepsie would never be daylighted, since the rock is armor-grade granite and the ridges are very tall and thin.
The tunnels at Gallitzin, at the summit of the grade that includes Horseshoe Curve, were opened up to accept modern loads but not daylighted - they are a little too deep underground and the surface above is covered with houses...
Chuck
....I would say you hit on at least 2 of the reasons....Clearances {some cases}, and on going maintenance costs. I certainly would think RR's would be happy to not have any to contend with, if possible.
Quentin
Why would a railroad daylight a tunnel? Are tunnels high maintenance? Maybe for added clearance...Tunnels offer natural protection..from rock and snow avalanches..no?
Our community is FREE to join. To participate you must either login or register for an account.