. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools . begin at the bottom of the tie in-stead of at a point about 2 inches below the top of the is done in order to prevent water from accumulatingaround the end of the tie in a material which is less permeablethan the other forms of ballast. In Fig. 112 are shown two cross-sections for ballast for roadsbelonging to Class C. On roads of this class it is assumedthat crushed rock will not be used for ballast. The width ofroadbed between shoulders is 14 feet, while the depth of
. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools . begin at the bottom of the tie in-stead of at a point about 2 inches below the top of the is done in order to prevent water from accumulatingaround the end of the tie in a material which is less permeablethan the other forms of ballast. In Fig. 112 are shown two cross-sections for ballast for roadsbelonging to Class C. On roads of this class it is assumedthat crushed rock will not be used for ballast. The width ofroadbed between shoulders is 14 feet, while the depth of ballastunderneath the tie is 6 inches. It should be noticed that the above sections issued by theassociatioa do not include any cross-section which is recom- J 272 RAILROAD CONSTRUCTION, §235. mended when no special ballast is used other than the naturalsoil. In such a case a cross-section very similar to the sec-tions shown for cementing gravel and chert should be used. Theessential feature of such a section is that the soil, which isprobably not readily permeable, should be kept away from SLDPEj^Vo THE FOOT. GRAVEL, CINDERS, CHATS, ETC.
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