Geology Reference
In-Depth Information
Box 11.3
PROBLEMS OF DEVELOPMENT ON PERMAFROST
Buildings, roads, and railways erected on the ground
surface in permafrost areas face two problems (e.g.
French 1996, 285-91). First, the freezing of the ground
causes frost heaving, which disturbs buildings, foun-
dations, and road surfaces. Second, the structures
themselves may cause the underlying ice to thaw,
bringing about heaving and subsidence, and they may
sink into the ground (Plate 11.9). To overcome this
difficulty, the use of a pad or some kind of fill (usu-
ally gravel) may be placed upon the surface. If the
pad or fill is of the appropriate thickness, the thermal
regime of the underlying permafrost is unchanged.
Structures that convey significant amounts of heat to
the permafrost, such as heated buildings and warm oil
pipelines, require the taking of additional measures.
A common practice is to mount buildings on piles,
so allowing an air space below between the build-
ing and the ground surface in which cold air may
circulate (Colour Plate 14). Even so, in ground subject
to seasonal freezing, the pile foundations may move,
pushing the piles upwards. In consequence, bridges,
buildings, military installations, and pipelines may be
damaged or destroyed if the piles are not placed judi-
ciously. Other measures include inserting open-ended
culverts into pads and the laying of insulating matting
beneath them. In addition, where the cost is justified,
refrigeration units may be set around pads or through
pilings. Pipes providing municipal services, such as
water supply and sewage disposal, cannot be laid under-
ground in permafrost regions. One solution, which was
used at Inuvik, in the Canadian North West Territories,
is to use utilidors. Utilidors are continuously insulated
aluminium boxes that run above ground on supports,
linking buildings to a central system.
The Trans-Alaska Pipeline System (TAPS), which
was finished in 1977, is a striking achievement of con-
struction under permafrost conditions. The pipeline is
1,285 km long and carries crude oil from Prudhoe Bay
on the North Slope to an ice-free port at Valdez on
the Pacific Coast. It was originally planned to bury the
Plate 11.9 Subsidence due to thawing of permafrost, Dawson, Klondike, Alaska, USA.
( Photograph by Tony Waltham Geophotos )
Search WWH ::




Custom Search