]
=======================================================
8
-------------------------------------------------------
Methods and conditions.
-------------------------------------------------------
Top heading and bench. Muck loaded by hand.
" " " " " " " "
Double heading and bench. Muck loaded by steam
shovel. Stretches aggregating 200 ft. narrowed
to about 25 ft. and later enlarged are included.
Excavation about 30 ft. wide. Top full-width heading
and bench. Muck loaded by hand. Steam shovel
not installed.
Excavation about 30 to 35 ft. wide. Top full-width
by hand and part by steam shovel.
Double heading and bench. Part of the muck handled
by hand and part by steam shovel.
Exploration drift about 10 ft. by 13 in. Muck loaded by
hand. 14 ft. timbered.
At portal of twin tunnels. Drift excavated to full
width and bench. Muck loaded by hand. 12 ft.
timbered.
Drift excavated to full width and bench. Muck loaded
by steam shovel. Full-width tunnel timbered for 26
ft. independently of the main excavation.
=======================================================
THREE-TRACK TUNNEL EXCAVATION.
When it became evident that the work through the Fifth Avenue section
would be extremely slow, shafts were sunk in each street between Sixth
and Seventh Avenues.
Pages:
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48