There was considerable
subsidence in the tunnels during construction and lining, amounting to
an average of 0.34 ft. between the bulkhead lines. This settlement has
been constantly decreasing since construction, and appears to have been
due almost entirely to the disturbances of the surrounding materials
during construction. The silt weighs about 100 lb. per cu. ft. (this is
the average of a number of samples taken through the shield door, and
varied from 93 to 109 lb. per cu. ft.), and contains about 38% of water.
It was found that whenever this material was disturbed outside the
tunnels a displacement of the tunnels followed. The tunnels as above
noted have been lined with concrete reinforced with steel rods, and
prior to the placing of the concrete the joints were caulked, the bolts
grummeted, and the tunnels rendered practically water-tight; the present
quantity of water to be disposed of does not exceed 300 gal. per 24
hours in each tunnel 6,100 ft. long.

_Bergen Hill Tunnels._--These are two single-track tunnels, 37 ft. from
center to center, and extend for a distance of 5,940 ft. from the
Weehawken Shaft to the Hackensack Portal. They were built almost
entirely through trap rock. The contract was let on March 6th, 1905, to
the John Shields Construction Company, but was re-let on January 1st,
1906, to William Bradley, the Shields Company having gone into the hands
of a receiver. About 1,369 ft. of the tunnel excavation was done by the
Shields Company, but no concrete lining. The maximum monthly progress
for all headings was 622 ft., and the average progress was 338 ft. A
working shaft 216 ft. deep was sunk from the top of the hill, to
facilitate construction. The tunnels are lined with concrete throughout.
Typical cross-sections of these tunnels are shown on Plate VIII.

In conclusion it may be admissible for the writer after having, in
conjunction with Mr. Samuel Rea, experienced the evolution and
materialization of this Pennsylvania Railroad scheme, to express his
great sorrow for the untimely death of the father of the entire scheme,
the late President Cassatt.

End of the Project Gutenberg EBook of Transactions of the American Society
of Civil Engineers, vol. LXVIII, Sept. 1910, by Charles M. Jacobs

*** END OF THIS PROJECT GUTENBERG EBOOK SOCIETY OF CIVIL ENGINEERS ***

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