Pogledaj jedan post
Old 13.01.2007., 11:48   #62
Naravno i dalje:

The first step in construction would have been to lay the ground
course. This process would have consisted in placing large blocks
with great precision to establish the dimensions of the pyramid. Based
on a survey reported in the literature, the base is square and is
oriented to the four points of the compass to standards that would be
challenging to a builder today. Construction would have proceeded to
add layers above the base, until the next "step" was achieved. Here
the structure would have been carefully leveled again. It would not
have been necessary to level each layer, as this would have increased
the amount of cutting and trimming on each block and would have
wasted material. It is believed that there are 14 to 16 layers per
step and 15 to 17 steps.

We assumed that construction was based on three components: the outer
casing stones—carefully dressed white Tura limestone; an inner layer
of "backing stones"; and the core blocks of Giza limestone, which
were not dressed accurately but were fitted into the inner volume of
the pyramid and then leveled only at the next step (not every course).
Irregular shapes were incorporated into the structure to maximize the
use of available materials. Casing blocks would be field dressed so
as to fit accurately next to and on top of their adjoining blocks.

We considered many concepts to understand how the Egyptians were able
to raise blocks to a height of 481 ft (147 m) with the limited tools
available. We assumed the use of rollers but not wheels or pulleys.
To evaluate the ramp issue we first constructed several mathematical
models that computed the number of blocks per layer and the volume,
height, and other measurements of the blocks. We know the blocks are
not of uniform dimension—that the lower blocks are thicker by as much
as 5 ft (1.5 m) while the thickness drops to 2 ft (0.6 m) or less
near the top. Not having a survey of typical sizes, we made a series
of calculations based on average sizes (see illustration).

Our calculations convinced us that most of the ramp concepts would
have been impractical because they involved a construction effort
greater than that required for the pyramid itself. We assumed that
the Egyptians would not commit resources to building anything more
than minimally required given the fact that the ramp had to be
demolished at the conclusion of construction. The literature reports
that the Great Pyramid is constructed of 2.3 million blocks and that
each weighs on average 2.5 tons (2.3 Mg). Our review found no basis
or origin for these numbers, which have been widely quoted. We made
our own estimates, assuming various dimensions and a specific weight
for limestone of 160 lb/cu ft (2,563 kg/m3). These calculations
showed that there could be from 2 million to 2.8 million blocks,
depending on the assumptions. We then refined the calculations to
deduct for the void volume of corridors and chambers, subtracted an
allowance for granite used in lintels, the capstone, and ceilings,
and treated the finish layer separately. This suggested that the basic
building blocks numbered about 2 million, based on average dimensions
of 3 ft (0.9 m) wide, 3.5 ft (1 m) high, and 4 ft (1.2 m) long. ------

Inspection of our mathematical model showed that at the point that
layer or level 50 had been reached essentially two-thirds of the
blocks had been put in place. This suggests that a single large
ramp—to one face of the pyramid—would have been feasible. This ramp
would have been 175 ft (23 m) high and more than 1,000 ft (705 m)
long and would have had a grade of 15 percent—which we assumed as an
upper limit. Also, it would have contained 30 percent of the volume
of the pyramid itself. The ramp dimensions would have been influenced
by the construction schedule. To construct the pyramid on a
reasonable schedule the ramp would have had to be wide enough to
enable multiple teams to approach the working surface, deliver their
loads, and leave without hindering other workers.

Ultimately we settled on a hybrid ramp scheme. There was a single
ramp on one face of the pyramid up to level 50, from which a series of
ramps wrapping around the pyramid reached level 120. These ramps
would have been much narrower and supported by the pyramid itself and
thus could have been constructed with much less material. We
hypothesized that the blocks in the last two (outer) courses were
left out near the corner to create a takeoff point wide enough for the
primary ramp. The secondary ramps would have been used at an
elevation at which the horizontal distance was long enough for a
significant gain in elevation.

We assumed that a third method was used above this point: the
"staircase" left in the center of the construction at the very top.
The blocks for the peak would have been pushed manually from below
and pulled up by ropes over poles or bearing stones up this staircase
and then put in place. At this point the number of blocks required is
only about 7,000 for the last 20 layers. Once the capstone had been
maneuvered into place the staircase would have been filled in from
the top down to the platform level at the end of the last ramp.

An interesting possibility to consider is that the capstone might
have been brought up to the last level that was reachable by a ramp
and then jacked up as the balance of the pyramid was constructed—that
is, the pyramid was built beneath it and it rose with the remaining
levels.

The pyramid was finished with white limestone casing stones from the
quarry across the Nile River at Tura. We assume that the finish
blocks were brought by ship to Giza. These blocks were carefully
placed, then trimmed after placement to provide a smooth exterior
surface. Using the same model to calculate the number of finish
blocks that we had used to determine the number of blocks per layer,
we determined that the number was approximately 53,000.

We assumed that scaffolding was erected at the top levels to position
these blocks and that the work proceeded upward course by course.
Because the topmost blocks were half the size of the regular blocks,
they could be positioned by hand. Once the work reached the top of
the pyramid any missing blocks were filled in down the staircase and
any finishing touches were performed. As layers were completed the
ramp was gradually removed.

We determined that there were 3 workweeks of 10 days per month—8 days
of work followed by 1 to 2 days off. A workday consisted of four to
five hours in the morning followed by four to five hours after lunch.
Deductions would be necessary for holidays and religious observances,
so we used 280 working days per year as our estimate for construction
time.

We estimated that a delivery rate of 180 blocks per hour was required
from level 50 to level 74 and then used this rate to determine if the
ramp size and number of crews were feasible. This seemed possible. We
then determined that at the lower level the ramp would be wider and
could sustain delivery rates twice this number. Above level 75 the
delivery rate drops off because of the smaller number of blocks, so
ramp size and crew numbers are reduced. The size of crews can be
estimated in various ways. Carrying capacity will ultimately depend
on load and distance. We assumed an average crew of 20 men.

This detail indicates how casing stones were cut to the proper angle.
Unit cost estimates were developed from a variety of sources,
including the team's judgment and experience. For example, our
stonecutting estimate of two man-days per block is based on our
judgment. For the average block we assumed that a team of 20 laborers
was required to pull a sled up the ramp and onto the work area. This
would require four hours on average (up to level 50), which meant
that a team could move two blocks per day. Ten man-days were required,
therefore, to move each block into place.


For estimations regarding excavation and ramp construction, we
consulted turn-of-the-century civil engineering handbooks and
established unit rates for moving earth manually. This corresponded
to about 1 cu yd/h (0.8 m3/h), with time added depending on the
distance the material was carried. We estimated that at an average
distance the rate was 0.03 d/cu ft (0.1 d/m3). We also prepared a
manpower labor forecast. Once courses 1 through 50 were completed the
labor requirements dropped off considerably; additionally, the
skilled labor requirements are consistent with a workers' village of
4,000 to 5,000 persons on-site. The total labor expended is 36.7
million days, or approximately 131,200 man-years. Thus the average
labor force over the 10-year duration of the project is therefore
13,200 men.
__________________
Sumnjaju neki da nosi nas pogresan tok
lampandina is offline  
Odgovori s citatom