EARTHWORK.-THE FOUNDATION.
In the projection of a railroad-line engineers endeavor so to utilize the principle of compensation in the moving of the rock and the earth that the material from the cuttings shall furnish as nearly as possible the amount required to form the embankments.
Earthzcork: Embankments and earthwork, as it will form the foundation of the road-bed and the permanent way, should be uniformly solid, of ample width, with gentle slopes, and with provision for thorough drainage. The several forms which the earthwork may assume are the embankment (pi. 24, figs_ 1, 2), the cutting (fig. 3), and the side cutting (p. 26, fg. 13). It will often happen that the masses removed in excavations cannot be used for the embankments, as when the material is not suitable for such use, when the distance from the cut to the embank ment is too great, or when the transfer of the material is impeded by un finished works (bridges, tunnels, etc.). But when, as is commonly the case, cuttings and embankments follow one another in rapid succession and the excavated material is suited for the purpose, it will be found advan tageous to form the embankments, as far as possible, of the materials re moved in the cuttings.
According to the nature of the ground, the work in a cutting is carried on with the shovel, p.ick, and crowbar, or by blasting- with gunpowder, dynamite, etc., the high explosives being now generally employed upon hard and compact rock.
Cuttings: Disioosing of means to be adopted for remov ing the loosened and broken material will be determined by its quantity, the distance to which it must be transported, and other considerations. Thus, for comparatively short distances, wheelbarrows will be most ser viceable; for greater distances, hand-tilting or dumping-cars (fi/. 24,figs. 6, 7), that may be tipped to an angle of 45°. In these cases planks are laid down to serve as a track for wheeling,r or rolling the load. As the dis tance increases, dumping-cars drawn by horses are substituted, and a tem porary railway laid upon longitudinal strips or sleepers is commonly pro vided for the cars to run upon (fig. ga–c). Filially, when considerable
masses of earth or rock are to be removed, the locomotive must be pressed into service (fig. 5). According to circumstances, the work of cutting may be started either from the middle or from the sides, and proceed regularly downward to the proper level in a series of benches or terraces. In plan ning- such work it is important to locate the burden-road in such relation to the work being- carried on that the loosened material may be loaded on the dumping-cars as directly as possible.
most advantageous grade for burden-roads is : Too, since on such an incline the loaded cars will just about run down by their own weight. In deep cuttings, however, especially at the commencement of the work, it will be impossible to avoid steep grades. In such cases it will often be advantageous to convert the declivity into an inclined-plane railway (of from 16 to 5o per cent. grade), upon which the loaded cars in descending draw up the empty ones by means of a cable passing over a fixed drum or pulley. Where, on the other hand, it is necessary to remove material from the depths of a cutting to high ground at the side, the inclined plane will likewise be employed, with the provision of a station ary steam-engine at the summit to furnish the power for drawing- up the loads.
Sysions of S (pl. 24) illustrates a method of making deep side-cutting-s at one time practised in England. In this, the work men with their barrows are drawn up the slope by horse-power. This method, however, has fallen into disuse on account of the liability of the roadway to become dangerously slippery. Another system of cutting, which may occasionally be followed advantageously consists in driving a lateral tunnel or gallery at the bottom of the proposed cutting, and sinking from the top, at several convenient points, vertical shafts to communicate with the gallery. These shafts are gradually enlarged—funnel-shaped—and the loosened material is allowed to drop through them directly into the trans port-cars stationed in the gallery below to receive it.