Timbering was required for a depth of
only 10 ft. below the surface of the ground.
A drift, 30.6 ft. long, 17 ft. wide, and 27 ft. high, connected the
south end of the shaft with the tunnels. The drift was excavated in
three stages, a top heading and a bench in two lifts. While blasting the
cut in the top heading, there was enough concussion to break glass in
the neighboring buildings. The use of a radialax machine reduced the
concussion somewhat, but it was very quickly abandoned on account of the
length of time required for the drilling.
The construction of the 32d Street Shaft was quite similar to the one on
33d Street. It was 31.5 ft. long, 20.5 ft. wide, and 71 ft. deep. The
depth of earth excavation averaged 19.5 ft. The rock in this shaft was
seamy and not quite as hard or dry as that in 33d Street, and timbering
was required for practically the full depth to the crown of the drift.
Sinking was started on May 15th, 1905, and was completed on October
26th, 1905. The daily average rate was 0.30 ft. in earth and 0.52 ft. in
rock. The drift was excavated in much the same manner as the one in 33d
Street, but the rock being softer the radialax machine was not used.
TUNNEL EXCAVATION.
During the early part of the work, the contractor devoted his entire
attention to the work of excavation.
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