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Geotechnical News • September 2013
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GEOTECHNICAL INSTRUMENTATION NEWS
were evaluated against those obtained
using traditional instruments. This
article presents the results of the fourth
site, where an INC500 Series In-Place
Inclinometer (INC500) from GEO-
DAQ was installed vertically to obtain
data from a landslide in a remote
location along the Dalton Highway in
northern Alaska.
Research site and installation
Geology and background
In recent years a new permafrost-
related hazard has affected Alaska’s
Dalton Highway in the southern
Brooks Range. Near Mile Post (MP)
219, an elongated lobe of frozen soil,
rock, and debris – termed a frozen
debris lobe (FDL) – is encroach-
ing on the highway. Many FDLs are
present within the Dalton Highway
corridor; however, near MP 219, the
critical FDL-A is less than 60 m from
the highway shoulder. Analysis of
remotely-sensed imagery indicated
that FDL-A moved at an average
rate of 1.0 cm per day between 1955
and 2008, and reconnaissance site
visits suggested several movement
mechanisms, such as permafrost creep,
debris flows along the over-steepened
toe, and basal sliding (Daanen et al.,
2012). Prior to a 2012 field program,
however, we did not know anything
about the lobe’s internal structure, nor
did we have any in situ movement
measurements. We also suspected that
FDL-A might move quickly enough
so as to make retrieval of the M-IPI
device impossible. Thus, the reasons
for this installation were 1) to collect
important data to determine FDL-A’s
mode, location, and rate of movement,
and 2) to determine how much move-
ment the INC500 device could with-
stand before it no longer functioned.
Instrument installation
The author, working with colleagues
from the Alaska Department of
Transportation and Public Facilities
Figure 2. Installing the INC500 within the guide casing (photograph courtesy
of J. Simpson).
Figure 3. Cumulative displace-
ment measurements for the boring
through FDL-A until the INC500
began to demonstrate signs of
failure.