Building, construction and megacities
Underground development may be
diffi cult in countries such as Holland,
where the groundwater table lies close
to the surface.
below ground up to three storeys deep to rise buildings and existing underground realistic depreciation times were applied
protect themselves from the heat but also infrastructure like public transport systems. in calculating the deteriorating value of a
to hide from hostile tribes. In Medieval Another is the exorbitant price of land above given construction over time, underground
times, underground construction was often ground in the heart of a city. construction might turn out to be more
related to war, such as the construction of The desire to escape cold winters or economical than one above ground.
secret underground passages to escape hot summers and to save energy can be Underground constructions in or close
undetected from besieged fortresses. another motivation. Concentrating services to the solid rock face may also be the
In the second half of the 19th century, on several underground levels avoids the best solution for coping with seismic
the construction of tunnels was vital to need to travel great distances. Underground risks. Thick layers of soft deposits may
the rapid expansion of railway systems in public transport systems also reduce the use strongly accelerate seismic waves, thereby
mountainous areas. Meanwhile, lack of of private cars, limiting air pollution and the contributing to the destruction of structures
space caused cities like New York, Paris congestion of roads. Underground cities are on the surface.
and London to develop underground public also energy-effi cient in other ways. The air
transport systems that other large cities temperature remains quite constant below Possible diffi culties
have since emulated. ground, increasing only slightly with depth. One potential problem underground
Thus, much less energy to heat or cool is cities may encounter is the presence of
»Since the turn of the
required than is the case above ground groundwater. Much of the aptly named
where temperatures can be more extreme Netherlands lies below sea level. In many
century, underground – as hot as 50°C in New Delhi and as cold Dutch cities, the groundwater table is quite
construction has been
as 40°C below freezing in Québec (Canada) close to the surface. That may seriously
expanding rapidly.
– as well as varying considerably with the hamper construction of underground
seasons. structures. In other cities, the groundwater
Cost is another factor. There is no need table may be high only in places, as in
Underground cities to be concerned about the appearance of London which is situated on the River
The decision to opt for an underground underground buildings, as no-one will be Thames.
shopping mall as opposed to one above admiring the façade. Thus, the exterior of Since the turn of the century, underground
ground can be driven by a combination underground constructions does not require construction has been expanding rapidly.
of factors. One is the proximity of high- regular maintenance. If longer and more This is particularly true in China,
90 PLANET EARTH www.yearofplanetearth.org
PE19.builingskj.mw.indd 90 16/2/09 11:39:49 am
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