Page 310 - Fundamentals of Geomorphology

PERIGLACIAL LANDSCAPES 293

Box 11.3

PROBLEMS OF DEVELOPMENT ON PERMAFROST

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