Environmental Engineering Reference
In-Depth Information
Preindustrial construction involved a skillful integra-
tion of large numbers of workers in order to accom-
plish tasks that appear extraordinarily demanding even
by modern standards, and yet many of these structures
were built in a very short time, the Parthenon in just
fifteen years (447-432 B . C . E .), the Pantheon in about
eight (118-125 C . E .). There is no mystery about how
these stunning structures were built (W. J. Anderson
1902; Coulton 1977; Adam 1994; Erlande-Brandenburg
1995). Massive stone components (Parthenon archi-
traves weighed almost 10 t) and large timbers were lifted
by compound pulleys or by cranes that were powered
by workers or animals turning capstans, windlasses, and
treadwheels. The Romans pioneered the use of concrete.
The Pantheon's bold dome (no preindustrial builders
ever topped its 43.2-m span) consists of five rows of
square coffers of diminishing size that converge on the
central oculus (MacDonald 1976). Its most intriguing
property is the vertical decrease of specific mass achieved
with progressively thinner layers of a lighter concrete
(Mark 1987). Builders of medieval cathedrals and castles
included many craftsmen using specialized tools (Fitchen
1961; C. Wilson 1990; Courtenay 1997).
In contrast to the well-known building techniques that
were used in antique temples or medieval cathedrals, the
logistics that made it possible to erect massive structures
such as prehistoric megaliths and stone pyramids are
speculative. There is no doubt that wooden sledges or
rollers, ramps, and massed labor were used to move
heavy stones or statues. Two Assyrian bas-reliefs from
Kuyunjik (c. 700 B . C . E .) show giant statues moved on
wooden sledges with about 50 men pulling, 10 operating
a large lever at the back, and another 10 or so laying and
raising logs and wedging a large lever. In brief spells such
groups could develop about 14 kW of useful power. A
better-known Egyptian painting of transporting a 50-t
colossus from a cave at el-Bersheh (1880 B . C . E .) depicts
127 men (peak useful power of over 30 kW) pulling a
sledge whose path is being lubricated by a worker pour-
ing water from a vessel (fig. 7.9).
Protzen (1993) determined that the heaviest of enor-
mous Inca stone blocks in the southern Peru, a 140 t
stone at Ollantaytambo, required the force of 120.4 t to
be pulled up the ramp, an effort calling for the con-
certed exertion of some 2,400 workers. The peak power
of this group would have been around 600 kW, but
we know nothing of the logistics of such an enterprise:
How were more than 2,000 workers harnessed to pull
in concert? How were they arranged to fit into the
confines of the narrow (6-8 m) Inca ramps? Most
intriguingly, construction of the three great pyramids
at Giza remains a matter of conjecture. There are no
contemporary descriptions or depictions of these proj-
ects. We know that the core stones were quarried near
the pyramid site, that limestone for the facing was
brought from Tura quarries across the Nile, that massive
granite blocks inside the structure were shipped from
southern Egypt, and that all this material had to be
moved up on a ramp to the building plateau (Lepre
1990; Lehner 1997).
We also know that very large stones were transported
on boats. A unique image from Deir el-Bahari shows
two 30.7-m-long Karnak obelisks carried on a 63-m-
long barge pulled by about 900 oarsmen in 30 boats
(Naville 1908). And Spence's (2000) demonstration of
how the pyramids were so near-perfectly oriented—using
the alignment of Mizar and Kochab, two circumpolar
stars, a method that also explains slight deviations in the
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