C. RAILWAY CONSTRUCTION
Railway Construction - Introduction
The selection of lines of railway is mainly governed by the same principles as hold good for roads, but the cost of the rails renders it of greater importance to shorten the length of the route than to make slight savings in embankments and cuttings. The first step in the survey is to ascertain the positions of the watercourse and watershed lines of the district to be passed through. The general direction having been selected by the help of an ordnance map, a sketch-map, or a special reconnaissance survey, the river-crossings are to be examined and decided upon, and the points determined at which the watersheds are to be crossed and the approaches to bridges set out. Trial lines should be run between the points thus fixed, and the country should be carefully examined on each side of these before the route is finally decided on. Sharp curves and steep gradients are in themselves evils, involving special cost for maintenance and for working, although original outlay may be economized by the adoption of them. A straight and horizontal surface is assumed as the standard of perfection; and the proper business of the engineer in laying out a railway is to harmonize the engineering and the financial conditions of the problem so as to yield the highest practicable return on the money expended, and to see that, whilst the railway may be neither quite straight nor quite level, it shall not be unduly costly in construction from excessive cutting, tunnelling, and making of embankments, in order to obviate severe curves and gradients, nor excessively cheap from following the surface of the ground too closely and incurring heavy gradients and severe curves, and as a consequence heavy working expenditure.
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Railway, Railways - Table of Contents