Geology Reference
In-Depth Information
Copper River railway has experienced similar maintenance problems while other rail lines
have been abandoned (Ferrians et al., 1969). The latest example comes from Tibet, where
a number of experimental studies were undertaken in the mid-1970s to evaluate the fea-
sibility of a railway across the plateau to Lhasa (Research Group on Experimental Roadbed
Research, 1979). For a substantial portion of its length the proposed route crosses rela-
tively warm and sometimes discontinuous permafrost (see Chapter 5). This major engi-
neering project was completed in July, 2006. In order to maintain a frozen roadbed, the
primary method adopted has been to construct an embankment that remains frozen
(Cheng and Li, 2003). Numerical simulation shows that the annual thawing rate of per-
mafrost, under natural conditions and assuming a ground surface temperature increase
of 0.025 °C/year, requires a minimum height of the embankment of
0.6 m for a 50-year
period of serviceability of the railway (Ling et al., 2003). In one area where ground-ice
bodies occur, duct-ventilation is being employed to keep ground temperatures below zero
beneath the railbed (Niu et al., 2003).
The construction and maintenance of airstrips is also costly in permafrost regions since
any slight heave or thaw settlement affects the runway grade. This is especially important
with the use of large jet aircraft in northern regions, for both freight and passengers. In
northern Alaska and Canada, gravel and rock-fi ll are used for most all-season airfi elds
(Crory, 1988) but, in response to the safety issue of grade, black-top (asphalt) surfaces are
now in place at large airports such as Barrow (Alaska), Inuvik, Yellowknife, Iqualuit
(Canada), and Longyearbyen (Svalbard). This enhances the possibility of thaw settlement
beneath the runway and increases the desirability of the runway subgrade to be of appro-
priate quality (i.e. composed of non-frost-susceptible aggregate) and suffi cient quantity.
At Inuvik, a program to monitor the progression of the frost-line was put in place follow-
ing back-coating of the runway in 1981-1982 (Johnston, 1982). In northern Russia, runway
maintenance is a little-discussed problem in the available literature. Because air transpor-
tation is vital to many northern settlements, to military usage, and to the support of
resource exploitation activities, the importance of sound permafrost engineering cannot
be underestimated. Recently, the US Federal Aviation Administration has requested that
this issue of pavement roughness due to frost heave be addressed as a safety concern
(Lenngren, 2000).
∼
14.7. OIL AND GAS DEVELOPMENT
The periglacial environment contains appreciable quantities of natural resources. In the
last 30 years, the major stimulus for much economic development in Arctic North America
and in northern Russia has been the exploitation and development of energy reserves,
notably hydrocarbons.
14.7.1. Exploration Problems
Some of the earliest exploration activity took place in northern Alaska in the late 1940s
in the US Navy Petroleum Reserve (NPR-4). At that time there was little understanding
of the sensitivity of tundra terrain to disturbance (Lawson et al., 1978). Drilling was
undertaken in both summer and winter months, vehicles were moved randomly across the
tundra, and waste-drilling mud was discarded at the site. Not surprisingly, long-lasting
terrain damage was incurred (see Figure 8.16A). Subsequently, in the 1970s, the Prudhoe
Bay oilfi eld was developed.
