Geography Reference
In-Depth Information
been a big psychological success which means that many residents take breaks to
sit in sunlight in the square, instead of just seeing the sunlight in the sky above, and
which has invigorated this site. A similar but smaller scheme was created in 2006
in the small village of Viganella, 120 km N.E of Turin in Italy, which was also
handicapped by a location in a deep valley. In this case a 40 m
2
polished steel mir-
ror reflects the sun and produces a more diffuse light over a wider area in the valley
bottom, at a cost of $ 160,000. The success of these schemes is likely to encourage
other northern towns to create similar projects to effectively extend the period of
limited sunlight in winter.
Finally, it must be emphasized that there are
specific problems of construction in
permafrost areas
where modern building techniques from southern climates have
proved inadequate, given the freeze-thaw problems that lead to cracks and subsid-
ence in roads and buildings. (Harris
1986
, pp. 80-98). The Central Housing and
Mortgage Corporation in Canada (CHMC) is one of the agencies in northern cli-
mates that have shown how many new engineering techniques have been used since
the 1960s to mitigate these effects, especially for housing developments. A popular
effective approach is the use of a thick gravel pad under buildings, preferably with
insulated polystyrene layers to keep the sub-layers frozen, with or without rigid
slabs above, upon which the building is built. The sinking of reverse T supports
or straight piles deep into the unfrozen permafrost zone are two other techniques
that can provide rigidity to the building structure, although it is always a essential
to have the floor of the building above ground, so that a zone for air to penetrate
lies immediately beneath the building, again to keep the surface layer as cold as
possible. Not surprisingly utility lines between buildings are almost always above
ground. Although it might be assumed that the biggest building problems lie in the
coldest areas of continuous permafrost, in practice the less severe northern zones
with longer periods of thaw-sensitive layers have greater maintenance costs. Since
they have greater periods of warmth in the surface zones, this affects the layers
below, leading to the soil heaving and collapse described in the previous section on
winter conditions. It is now recognized that in all areas with permafrost it is essen-
tial to understand the specific climate, soil and moisture conditions before designing
structures that are adapted to the local situation.
Similar difficulties exist with the construction of transport routes and airfields
where the use of insulated pads in a gravel surface above ground level is designed
to keep freeze-thaw at bay. Some idea of the scale of the learning-on-the-job that
is often involved in new northern construction projects can be seen in the fact that
the construction of the 1,300 km Alyeska pipeline across Alaska between 1969 and
1977 cost $ 7 billion to complete. This was eight times what was expected because
of the freeze-thaw problems in permafrost regions, for many parts of the pipeline
had to be built on supports and above ground. Indeed, until the 1960s there were few
all-weather roads or railway lines in permafrost areas. Even today in many parts of
the remote Russian and Canadian north many settlements are primarily served by
winter roads, either composed of compacted snow, or ice aggregates that are com-
pressed and then sprayed to create a winter consolidated road-bed. But new roads
and rail, albeit it with much shorter lives and greater maintenance, are being built
