[Illustration: Fig. 10. SKETCH SHOWING DIVISION OF LINING FOR PURPOSES OF CONSTRUCTION, AND NAMES OF SECTIONS]
An essential part of the agreement with the sub-contractors provided that the operations incident to the placing of the lining should be carried on so as to provide at all times space for a single track of 3-ft. gauge, running through the work, and the necessary clearance for the locomotives and cars used in hauling out the muck. A clearance diagram of one of the “dinkys” used in the tunnels, and its relation to the forms used, is shown by Fig. 12 and also by Fig. 16, the 4-yd. Allison cars, used for handling the muck, taking practically the same width, although they were not quite as high. This requirement and the limited space available must be kept in mind in considering the design finally adopted for the forms and plant required in placing the lining. It should also be kept in mind that, with the rolling stock used, there was only room for a single track through that part of the tunnel where any concrete had been built. As the concrete progressed, therefore, the length of single track was necessarily lengthened, and the problem of transportation was made increasingly difficult.
In working out a design for the bench-wall forms, another highly important and controlling factor, which had to be considered, was the arrangement of the conduit lines, as shown in the general cross-section.[2]
[Footnote 2: Plate VIII of the paper by Mr. Jacobs.]
The quantities of the various materials in the lining, per linear foot of tunnel, were as follows:
Concrete 7.64 cu. yd. Rock packing: Paid for 1.48 cu. yd. Outside standard section line 1.74 ” ” ------------ 3.22 ” ” Iron and steel 44.2 lb. Vitrified conduits 84.0 duct ft. Water-proofing 13.0 sq. ft. Flags 3.3 ” ”
_General Methods._--The lining was started at both ends of the tunnels before the headings were finally holed through, so that there was practically a separate organization at each end, each in charge of one of the members of the firm. The work at the Weehawken end was started first, and the plant and scheme of working adopted there was thoroughly tried out before the plant for the western end was built, consequently, the latter was somewhat more efficient, being designed in the light of the experience gained at the Weehawken end.