introduction to civil engineering
             the development of steel bridges
             modelling railway structures
             how we built the East Lyn Viaduct


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 provided.

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 railway

Swainley tunnel on the Leek and Manifold as it is now

old Colorado tunnel

Aberglaslyn tunnels
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