railway civil engineering
Dolgoch Viaduct - a painting by Richard Picton
Most narrow gauge railways were built in
regions where standard gauge would have been too expensive to contemplate.
Where possible, railways were surveyed to follow the contours of the
hills. Cuttings and embankments were also usually necessary. This gave
rise to a technique known as 'cut and fill'. Where insufficient fill was
available or an embankment was not possible, a viaduct would have to be
Tunnels are very expensive to build, so
often, cutting would be as long as possible. The longest tunnel for
narrow gauge is the Seikan Tunnel in Japan at 34.4 miles long! The first
tunnel across the Continental Divide was the 1772ft long Alpine tunnel
on the three foot gauge Denver and South Park Pacific Railroad.
the remains of the Alpine Tunnel
Tunnels would generally be cut to the
minimum dimensions with only sufficient clearance to account for the kinematic envelope of trains. The tunnels on the Festiniog Railway have
always restricted the possible size of rolling stock because of this. Long tunnels would
of course require ventilation shafts at regular intervals.
Depending upon the geology, some tunnels
could be left 'hewn out of the living rock'. Most required lining. This
accounts for why some tunnels have rough hewn portals and others are
built in brick, stone, timber or concrete.
a tunnel portal on the Saundersfoot
Swainley tunnel on the
Leek and Manifold as it is now
old Colorado tunnel
Nothing defines railway engineering more
than its civil engineering structures. Many survive decades after the
track was lifted. Often, the style of engineering was specific to one
particular railway company. The truss girder bridges of the Welsh
Highland Railway would be one such example.
Narrow gauge railways were usually built to
a price and major civil engineering structures were avoided where
possible. The largest structure on a narrow gauge railway in the UK is Chelfham Viaduct on the
Lynton and Barnstaple Railway.
Some spectacular structures were built
elsewhere. Spindly steel or timber trestles.
Lispole Viaduct on the abandoned Tralee and Dingle Railway
It is surprising how many small
bridges have to be built to allow passage of a railway. These are mostly
for roads that pass over or under the tracks. Occasionally, there may be
an aqueduct or even a bridge for another railway. Bridges were nearly
always standardised by railway companies.
typical Reseau Breton bridge on the
Pempoul model railway - the cast iron railings were quite special
typical iron plate girder bridge on the
North Wales Narrow Gauge Railway