Table 2. Deployment analysis--November/December 1996.
Time
Tunneling
Production
Tunnel
on site
time
Progress
rate
length
Date
(hr)
(hr)
(m)
(m/hr)
(m)
Notes
11/22
12
3
4.6
1.5
12.2
Start in p.m.
11/23
11.5
8
7.6
1
19.8
11/24
9
4.5
1.5
0.3
21.3
Training day
11/25
12
10
9.1
1
30.4
11/26
19.5
4.5
5.5
1
35.9
Drill holes/redeploy
11/27
20.5
11
9.8
1
45.7
Fix pump/blown hoses
11/28
24
16
16.8
1
62.5
Drill holes/redeploy
11/29
20
15
15.2
1
77.7
Fix blown hoses
11/30
12
7
7.6
1
85.3
Genset problems
12/1
19
3.5
3.1
1
88.4
Drill holes/redeploy
12/2
20.5
17
21.3
1.3
109.7
12/3
12
4
6.1
1.5
115. 8
Finish in a.m.
tem simplification since the initial deployment has
resulted in increased productive time and produc-
RESULTS
tion. A complete rebuild of the tunneler, transform-
The tunneling system as configured during the
ing it from a prototype to a "preproduction" sys-
January 1996 deployment was capable of operat-
tem, is recommended, but budgetary constraints
ing at an average production rate of just over 1
will probably exclude this option. In either case,
m/hr, one-third of the target production rate. The
the South Pole Tunneling System is the first total
maximum sustained production rate (>4 hr) was
system capable of machining tunnels in the upper
1.5 m/hr. The maximum operating depth was ap-
region of an ice cap.
proximately 16 m from surface to floor, 6 m greater
An economic analysis of the system is prema-
than the design depth. Maximum total linear run
ture at this time, as CRREL is still working with a
for snow transport was 59 m, including an 18-m
prototype system that needs optimization. The
lift from the tunnel floor to the eye of the centrifu-
original analysis called for a production rate of ap-
gal blower fan. The maximum length tunneled
proximately 3 m/hr to be more cost-effective than
during one shift was 13 m, and the maximum one-
a cut-and-cover system. Therefore, on a direct dol-
day progress was 21.3 m. Approximately 54% of
lar comparison, the tunneling system as it stands
the shift time was devoted to productive tunnel-
is not economically feasible. However, that analy-
ing operations. The remainder was absorbed in
sis was based on a crew of eight personnel,
preparations for moving the equipment, prepar-
whereas we found that operating with three to four
ing vertical holes, equipment repair, downtime
is possible, albeit a good deal more strenuous. If
due to meals, and training. Table 2 summarizes
the production rate can be doubled to 2 m/hr, tun-
the tunneling activities of November through De-
neling should be competitive with other methods
cember 1996.
of forming tunnels. In any case, the use of tunnels
for passage and utilities is clearly preferable over
surface structures from the standpoint of safety and
maintenance of equipment, especially in winter.
CONCLUSIONS
The unlined tunnel machined in 1996 is cur-
The CRREL South Pole Tunneling System is a
rently being utilized at the South Pole Station for
workable option for creating tunnels at the South
the wastewater outfall line (Fig. 23). Shortly after
Pole. The system as deployed in 1996 had some
the installation of the line, during the 199697 win-
serious drawbacks, most of which were addressed
ter-over period when the Station was isolated from
either during the tunneling operations or during
physical contact with the outside, the outfall line
subsequent modifications made in McMurdo Sta-
failed. At the time, wind chill on the surface was
around 70 C and daylight was limited. The re-
tion in 1998. As with any prototype, the flexibility
built into the system added greatly to its complex-
pairs were quickly made to the line in the lighted
tunnel (at 40) without personnel having to ven-
ity and thus its susceptibility to breakdown. Sys-
21
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