. Railroad structures and estimates . 68 TYPICAL SECTIONS OF TUNNELS. ft. long at the west end and 27 in. thick and 1,288 ft. long at theeast end. In addition, on account of the spalling of the rock,some concrete lining may be required in the solid-rock section atthe west end. Typical sections of the tunnel, with its timbering and concretelining, are shown in Fig. 5. The timbering in the glacial driftconsists of a semi-circular roof arch supported on 12 X The timber sets are usually spaced 18 in. c. to c, but areset close where the material is loose and contains water. The archhas
. Railroad structures and estimates . 68 TYPICAL SECTIONS OF TUNNELS. ft. long at the west end and 27 in. thick and 1,288 ft. long at theeast end. In addition, on account of the spalling of the rock,some concrete lining may be required in the solid-rock section atthe west end. Typical sections of the tunnel, with its timbering and concretelining, are shown in Fig. 5. The timbering in the glacial driftconsists of a semi-circular roof arch supported on 12 X The timber sets are usually spaced 18 in. c. to c, but areset close where the material is loose and contains water. The archhas five or seven segments, usually single, but sometimes double. An interesting feature is that for the lined section in loosematerial the heavy footings of the side walls are braced by rein-forced-concrete struts 20 ft. apart. These are 18 in. wide, 24 at the ends and 18 in. at the middle. They are formedmonolithic with the footings and with the longitudinal concreteslab for the support of the track drain.
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Keywords: ., bookcentury1900, bookdecade1910, bookidrailroadstructur00orrouof
