Before evaluating the engineering methods used in cold regions, it is worth identifying where these regions are and why humans should want to build there.  Money (1980) defines the cold regions of the world as those that are permanently covered with ice, mainly the Arctic and Antarctic Circles at 66°N and 66°S respectively, and the adjacent periglacial areas marked by perennially frozen ground, or permafrost.  It is these periglacial areas that concern us, as this is where most of the human development in these regions takes place.  Figure 1 shows that periglacial areas include Alaska, northwest Canada, northern Scandinavia and Siberia.
 
 

The dominant reason for wanting to develop these places is economic.  The Klondike Gold Rush of 1898 and more recently, the discovery of large quantities of oil and gas in these regions has seen the construction of towns, industrial plant and pipelines in Alaska, Siberia and northwest Canada (Briggs et al, 1997).  The following paragraphs will briefly look at the landforms and engineering problems associated with the periglacial environments and then the methods used in Alaska and northwest Canada (see Figure 2) to overcome them.  The evaluation will be based on how well the methods used have supported and sustained human development and how much damage has been done to the local environment.
 
 

The main physical characteristics of periglacial regions relate to permafrost and ice.  The implication of the word permafrost is that it is permanently frozen ground.  However, the active layer of soil freezes and thaws depending on the season, whilst the thickness of the underlying permafrost is affected by the type of surface cover and the surface temperature (Williams, 1979).  Water increases by 9% in volume when it freezes and when frozen in soil, acts in a particular way also.  It is drawn to the point where the freezing is happening and layers of ice, called lenses are formed.  This process coupled with thawing can break-up roads and rupture pipelines (Money, 1980).   The widespread thawing of permafrost is called thermokarst and results in ponding, subsidence, soil strength loss and frost heave.   The problem for engineers is that thermokarst also occurs when natural vegetation is removed and a heated building is placed directly on permafrost affected ground instead.  The result is subsidence and distorted buildings (Briggs et al, 1997).  The other physical characteristics of periglacial regions include patterned ground, solifluction and ice wedges.  However, the significance of these is not necessarily the features themselves, but “the great forces indicated by the movements of soils, stones and boulders” (Williams, 1979: p14).  Consequently, it is essential that engineers know the geology, soil and climate of these regions before designing and building structures in them.  Unfortunately, the buildings of the early to mid part of the 20th Century were built with little of this understanding (Williams, 1979).

 The native peoples of North America were traditionally nomadic and lived in simple structures that they either abandoned or took with them when they moved on (Minority Rights Group, 1994).  It was their mobility, rather than any technology, which protected their homes and environment.   The gold rush in the Yukon, however, drew people to the region that wanted permanent structures (Williams, 1979).

The first buildings in the Yukon were built to the same design as many southern Canadian towns.  Massive timbers were laid directly on to the surface as foundations and the buildings constructed of timber.  The result was that the heated buildings melted the permafrost below them and caused subsidence as the active layer settled.  Basement walls made from concrete became displaced and cracked as the ice meted around them, whilst winter freezes ruptured water and sewage pipes.  Most of the buildings of this era have long since fallen down, having suffered from the subsidence and tilting caused by the thawing of the underlying permafrost.  Some towns, such as Aklavik, were abandoned altogether (Williams, 1979).  The engineers failed to realise that the removal of vegetation and the loss of heat through foundations caused the permafrost to melt and the thickness of the active layer to increase.  The result was subsidence and settling of soils (Briggs et al, 1997).  The engineers failed to understand the environment that they were working in and so damaged it.  The consequence of the damage was that their structures were unable to withstand the conditions.

 The Second World War and the need to build airfields, oil pipelines and military bases meant that expertise was accumulated on where to place and how to build structures.  Engineers began to understand the importance of choosing locations that were underlined with coarse gravels, well drained and had little ice (Williams, 1979).  They also began to realise that the natural vegetation itself helped to stop the permafrost thawing.   Aklavik’s replacement town, Inuvik was built on a well-drained site underlined by coarse gravels.  Coarse gravels do not suffer from frost heave, whilst good drainage reduces the amount of ground ice (Williams, 1979).  Smaller buildings are often built on 1-2m thick pads of sand and gravel with the wooden foundations placed on the pads.  The foundations support wooden columns designed to give a 1m space beneath the building.  This space reduces the amount of heat passed from the building into the ground and allows cold air to circulate beneath the building to cool the surface and prevent the permafrost from thawing (Briggs et al, 1997).   Wedges on either side of the building are used to counter the affects of heaving or subsidence.   Larger buildings, however, are usually built on top of steel or wooden piles driven into the permafrost.  Again, a space is left below the building to allow the movement of cooling airs (See Figure 3).  These methods have allowed engineers to build comparatively stable buildings using low tech and low cost techniques.
 
 

However, the need to provide domestic services and to build heavy industrial plant, oil pipelines and storage tanks has required a more scientific and high cost approach.

 To improve the provision of water and waste disposal, an above ground system of pipes carrying domestic water supplies, heating and sewerage was developed.  The system, called a Utilidor, consists of a raised box containing pipes (See Figure 4).  The box is insulated using aluminium and fibreglass cladding.  Because the Utilidor is insulated and not underground, it does not affect the permafrost and is not prone to the affects of ice-heave (Money, 1980).
 
 

The use of piles and stilts to raise a building above the ground is not always suitable for large industrial buildings, such as power stations and oil storage tanks (Briggs et al, 1997).  Stilts would not be able to support the size and weight of a power station and the amount of heat generated by such a facility could, despite the gap, cause the permafrost to thaw through heat transfer.   Figure 5 shows how engineers have used well draining sands and gravels to avoid frost heave and constructed air ducts below the building to allow cold air to circulate.  Foamglass under the floor also helps to insulate the building and reduce heat loss (Briggs et al, 1997).   These buildings use scientific knowledge to overcome building problems and protect the environment.  However, as Briggs (1997) points out much of the damage is done during construction itself.
 
 

Pipelines carrying oil and gas have also relied on an understanding of the environment and high tech solutions.  Perhaps the most famous periglacial pipeline is the Trans-Alaska Pipeline (TAP) which runs 1280km from Prudhoe Bay in the North to the ice-free Valdez in the South (Briggs et al, 1997).  The environmental conditions, distances involved and the fact that the oil had to be heated to flow in the pipeline gave the engineers some particular problems.  Their solutions had to prevent the permafrost thawing and reduce the potential of pipeline rupture.  The consequence of such an outcome would have been incalculable damage to the environment.
 
 

The oil pipeline is raised above the ground on a ‘vertical support member’ (VSM) which is inserted into the permafrost at a depth of 8m.  The engineers quickly realised that raising the pipeline above the ground would not be enough to stop the thawing of the permafrost so they added heat exchangers.  These devices use anhydrous ammonia and the process of evaporation to cool the ground around the

VSM in the winter.  The ground is cooled to the point that it does not thaw in the summer (Williams, 1979).  Where the pipeline is buried there should be little danger of thawing the permafrost, but are in any case insulated with a 10cm thick layer (Briggs et al, 1997).  The fact that the pipeline has been operating for over 20 years without a major rupture is a testament to the engineering methods used.  However, the estimated cost of US$900 million became nearly US$7 billion by the time of completion.

 The development of the cold regions of the world began with little regard to their geology, soils or climate.  Buildings were designed and built as if they were in more temperate climates, resulting in subsidence and tilting.  As engineers began to understand this new environment, they were able to introduce new methods that not only countered some of the problems, but also used the environment to their own advantage.  The placing of piles into stable permafrost and the building of towns on well drained gravels, for example.  However, the high cost of some building methods make the large-scale development of these regions prohibitive and whilst the buildings themselves may be environmentally friendly, much damage is done during the building process.

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