Geology Reference
In-Depth Information
Figure 14.2.
Diagram illustrating the effects of a gravel fi ll upon the ground-thermal regime and
thickness of the active layer. (A) Too little fi ll; (B) too much fi ll; and (C) the effects of (A) and (B)
upon the ground-thermal regime. From Ferrians et al. (1969), courtesy of the United States Geo-
logical Survey.
heated, the ground is being chilled. In the fi rst two years following installation, compari-
sons of predicted and measured temperatures at the top and bottom of the gravel pad,
and at the top of the ice-rich silt layer (Figure 14.3B, C), suggest the system works well
and permafrost continues to be maintained beneath the structure.
In instances where the structure concerned is capable of supplying signifi cant quantities
of heat to the underlying permafrost, as in the case of a heated building or a warm oil
pipeline, additional measures are frequently adopted. Usually the structure is mounted
on wooden or concrete piles which are inserted into the permafrost. Because an air space
is left between the ground surface and the structure, this allows the free circulation of air,
which dissipates the heat emanating from the structure. In Russia, where cities with popu-
lations greater than 100 000 were built in Soviet times and large buildings were erected,
construction usually took place on concrete pilings (Figure 14.4). Recent engineering
studies now predict increasing failure of these piles in the years to come. This is partly
because of warming permafrost (see Chapter 15, p. 388).
