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PLAN SHOWING METHOD OF MAKING JOINT BETWEEN ADJOINING SECTIONS. |
SECTION OF BENCH AND RETAINING WALLS
AND HALF ELEVATION OF PORTAL.
Hackensack Portal and Approach.
The approach cut at the western end is 300 ft. long, the alignment being a 2° curve, as shown in [Fig. 19]. The bench-walls and conduit lines built throughout the length of the tunnels are extended through the approach cut, the top of the former gradually sloping from the portal to the mouth of the cut, where they are just level with the top of the rail, the conduits also being depressed to the same relative position with the tops of the benches.
The top of the rock at the mouth of the cut, Station 327, was from 4 to 6 ft. below the top of the rail, and gradually rose through
the approach until at the portal it was about 6 or 8 ft. above the roof of the tunnel. The rock was covered with hardpan. A profile of this part of the work is shown on [Fig. 19]. The rock throughout the approach was water-bearing to a considerable extent, and a face-wall was built at the sides with free drainage, through rock packing and vitrified and cast-iron drains behind it, to keep this water from flowing over the tops of the bench-walls, and also to keep the lines of conduits dry.
The retaining walls were built in 25-ft. sections, the joints corresponding to those in the benches, being at the even stations, +08, +33, +58, and +83. V-shaped joints were made down the face, and the ends of the sections were made as shown by [Fig. 19]. The back part of the joint was mopped with hot pitch before the next section was built, so that there was practically no bond between any two adjoining sections.