. Costruzione ferroviaria, teoria e pratica; un testo-libro per l'uso di studenti in scuole universitarie e tecniche, e un manuale per l'uso di ingegneri in campo e in ufficio . COSTRUZIONE. § 129. taglia e deposita il materiale su argini bassi. I Suchmethods hanno il vantaggio di compattare gli argentidurante la costruzione e ridurre il ritiro futuro. Quando si utilizzano i carrelli, un argine di qualsiasi altezza può essere formato dallo scarico sull'estremità e dall'edificio a piena altezza (o anche più in alto per consentire il ritiro) mentre il embank-ment procede. Il metodo è particolarmente applicabile quando co-materiale
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. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . STRUCTION. § 129. cuts and deposit the material on low embankments. Suchmethods have the advantage of compacting the embankmentsduring construction and reducing future shrinkage. When carts are used, an embankment of any height may beformed by dumping over the end and building to the fullheight (or even higher to allow for shrinkage) as the embank-ment proceeds. The method is especially applicable when thematerial comes from a place as high as or higher than thegrade-line, so that no up-hill hauling is necessary. Only asmall contractors plant is required for all of these methods. Trestles capable of carrying carts, or even cars and loco-motives, from which excavated material may be dropped, arefound to be economical in spite of the fact that their cost is aconstruction expense. There is the disadvantage that suchembankments require a long time to settle, but there are theadvantages that the earth may be hauled by the train loadfrom a distance of perhaps several miles, dumped from the. Fia. 63. cars by train ploughs, or automatically dumped when thematerial is carried in patent dumping-cars, and all at a com-paratively small cost per cubic yard. The disadvantages ofslow settlement may be obviated, although at some additionalcost, by making the trestle sufficiently strong to support regulartraffic until the settlement is complete. During recent years cableways have been utilized to fillcomparatively narrow but deep ravines from material obtain-able on either side of the ravine. This method obviates theconstruction of an excessively high trestle which might other-wise be considered necessary. When an embankment is to be placed on a steep side hillwhich has a slippery clay surfacCi the embankment will some- § 130, EARTHWORK. 155 times slide down the hill, unless means are taken to prevent it
