Environmental Engineering Reference
In-Depth Information
into contact with the ground (Plate 24.4). For large buildings (industrial plant, power
stations, oil storage facilities, for example), it is necessary to ensure that the building is
on a thick pad of stable but well draining aggregate. In some instances the insulating
power of the pad is enhanced with fibreglass insulation, and by metal pipes running
through it which permit air to circulate in winter. Pads are also used to prevent permafrost
melting and land subsidence when roads, airport runways and railway tracks are
constructed. However, unsuitable construction techniques still lead to degradation of
ground ice, and it has been reported that a recently constructed railway line has shown
considerable distortion and buckling at Yamburg, western Siberia, only a year after its
completion.
The town of Inuvik, North West Territories, Canada, illustrates the problems of
construction in the tundra. A modern town of 3500 population was completed in 1961 as
a regional administrative centre. A hospital, a large secondary school, a diesel generating
station, oil storage tanks and the usual collection of shops, churches, hotels and
residences were built on terrain underlain by permafrost. An airport, road system and
river docks were also constructed. An innovative feature was the municipal Utilidor
system which carries the water supply, the heating pipes and the sewers in large
aluminium-clad units on wooden piles. In this way the pipes for the utilities do not have
to be buried in the sensitive permafrost. Figure 24.8 illustrates a variety of construction
techniques necessary in the tundra.
Over the years, considerable experience has accumulated on how to avoid the dangers
of abusing the sensitivity of permafrost terrain. However, many of the remedial measures
are high-tech and high-cost. In smaller villages with perhaps only single-storey
prefabricated buildings for housing, along with a school, a shop, a police station, a
mission and a nursing station, a low-tech and low-cost solution is necessary. Typically
the buildings are sited on pads of sand and gravel 1-2 m thick, placed on the original
ground surface with as little disturbance as possible. Upon the pads wooden blocks are
set to act as bearers for short columns which support the main joists of the building. In
some cases the joists may rest directly upon a number of bearers consisting of two large
opposed wooden wedges which can slide over each other when force is applied to one of
them with a sledgehammer. In this simple way subsidence or heaving movements in the
pad or ground beneath can be corrected by adjusting the wedges. Hence the building can
be maintained in a horizontal position if settlement occurs. Both the columnar and the
wedge arrangements ensure that an air gap, ideally
