Environmental Engineering Reference
In-Depth Information
mid's steep (51
52
0
) smooth slopes, wetted for easier
sliding, as inclined planes to pull the stones. These
assumptions led him to calculate the total labor force
needed to build the Great Pyramid at about 10,000 peo-
ple. In contrast, the oldest surviving account of pyramid
construction by Herodotus, written after the historian's
visit to Egypt two millennia after the structures were
completed, relates that the blocks were lifted from the
ground level by contrivances made of short timbers and
that a total labor force of 64,000 men was employed for
80 days a year for 20 years. Pliny put the total at 366,000
laborers.
Mendelssohn (1974), using basic physical con-
siderations including the average force in pulling a laden
sledge (10-15 kg/worker) and the labor needed to build
approach ramps, came up with 70,000 seasonal laborers
and up to 10,000 permanent masons. Wier (1996)
approached the problem of labor force by considering
the aggregate effort needed to lift all those stones above
the plateau. His calculation of the Great Pyramid's po-
tential energy is correct (2.52 TJ), but his assumption of
average daily work accomplished per worker (240 kJ) is
too conservative. After he factored in inefficiencies, he
ended up with the maximum labor force of less than
13,000 people. Assuming an average daily rate of just
0.25 m
3
of stone per worker, only about 1,500 quarry-
men using copper chisels and dolerite mallets and work-
ing 300 days a year were needed to cut 2.5 million m
3
of
stone in 20 years (the length of Khufu's reign). If three
times as many masons were needed to square and dress
the stones and move them to the pyramid site, the total
labor force would be about 5,000 people.
With net inputs of useful mechanical energy at 360
kJ/day only about 1,000 workers were needed to lift
the stone blocks. Doubling that number for the workers
7.10 Scaled oblique views, dimensions, and volumes of
Khufu's pyramid at Giza, Choga Zanbil ziggurat at Elam,
the Sun Pyramid at Teotihuacan, and the Jetavana stupa at
Anuradhapura. From Smil (1994).
needed to emplace the stones, and adding the labor
needed to build and repair sleds, ropes, and timbers and
to cook meals, adds to the total about 10,000 men,
clearly a manageable body. The gross inputs of useful
labor embodied in Khufu's pyramid (about 2.5 MJ/
worker
day) add up to some 150 TJ (fig. 7.10). For
comparison, Falkenstein (1939) calculated that the con-
struction of Anu ziggurat at Warqa required at least
1,500 laborers working 10 h/day for five years (em-
bodied energy
<
6 TJ), and E. R. Leach (1959) esti-
mated that the largest Anuradhapura stupa (fig. 7.10),
built of about 200 million of mostly rough-laid bricks,
needed only about 600 laborers working 100 days/a for
50 years (@7.5 TJ).
Some European cathedrals embodied a comparable
total of energy (5-10 TJ), others required considerably
