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Stair Steps to the Gods: Building the Great Pyramid At Giza
17 May 2009
Dr. Craig Smith is a professional engineer who has worked on a wide variety of very large engineering and construction projects during his career. His interest in the design and construction of the Great Pyramid at Giza stems from many years of experience managing large public works projects.
The Great Pyramid is the final resting place of the 4th Dynasty Pharaoh, Khufu, built for him by his Vizier, Hemiunu, who was also overseer of the courts, taxation and the king’s public works projects – and a cousin of the king’s. Hemiunu is buried in a tomb near that of his king.
A bit of history about Egyptian burial practices; the very earliest burials were in the desert sands. The first burial structures were covered with flat stones “mastabas” (the Arabic word for bench). During the reign of Djoser, a tomb comprised of mastabas built one upon the other, with each successive mastaba smaller than the one before, resulted in a stepped pyramid. It was not a difficult next step to conceive of a true pyramid. Seneferu, Khufu’s father, made several attempts at the construction of a true pyramid, but not until his third try was he fully successful. His first attempt at Meidum collapsed. His second – the Bent Pyramid – had too steep an angle and was on a poor foundation. As a result internal cracks developed which threatened to collapse it as well, so the angle was adjusted creating the signature bend in the sides. Not until his final effort – the Red Pyramid – did he succeed in creating a true pyramid. The internal chambers and passages ways have corbelled ceilings – the Egyptians did not know how to construct arches at this time – a technique which Hemiunu used in the construction of the Great Pyramid.
Contrary to popular opinion, the pyramids were constructed by paid workers – not slaves – many of whom lived at the site for their entire lives. The village where they lived has been revealed by the excavations of Dr. Mark Lehner. The village lies just south and east of the sphinx and the pyramid field. We know about the people who built the Great Pyramid due to the discovery of this village and the tombs where they were buried. Some of the surviving tombs were used by multiple generations of workmen. The village is laid out similarly to that of Deir el Medina on the West Bank at Luxor, the workmen’s village which housed the New Kingdom tomb builders.
The blocks of limestone used to construct the pyramid came from the area where the pyramid was built. The Giza Plateau’s bedrock is limestone, which provided both a firm foundation for the structure and an excellent source for building material. The stone was excavated and dressed using stone axes and copper chisels. The harder granite was cut using dolorite, a hard stone; samples have been found at the site of the abandoned “Unfinished Obelisk” in Aswan. The finished structure was clad with fine white limestone from the quarries at Tura on the east side of the Nile near modern day Cairo.
How was the pyramid actually constructed? Ramps. is the answer. The remains of construction ramps are still visible in many places in Egypt, including at Giza. A single ramp was used from the base until the completion of coarse #55 – about 1/3 of the height of the finished pyramid. By this point more than half the blocks required to construct the pyramid and all of the major interior beams were in place. Above coarse 55, no chambers were constructed. Thereafter, a ramp was built which encircled the pyramid. Using the lower courses for support, it snaked its way to within a few courses from the top. The last few stones would have had to be “manhandled” into place. Once the structure was complete, the white limestone casing was applied beginning at the top and working downward, and the construction ramp was demolished behind the stone masons as they worked their way down. Dr. Smith believes that the Egyptians had worked out the math related to the construction of ramps and were skilled at designing and building them. The pit formed by the quarrying of construction stone is still filled with thousands of pieces of ramp material which was pushed over the side to partially fill the hole once the pyramid was built and the ramps demolished.
In 2550 BC the Nile was much farther west than it is today - about ¼ mile from the base of the pyramid, so the ancients built a canal and harbor to facilitate bringing constructions materials almost to the foot of the structure.
The pyramid is oriented precisely north-south and east-west, and leveled to within a fraction of an inch, both horizontally and vertically. There have been a number of theories put forth over the years as to how the pyramid was laid out with such precision. Some have suggested that they sited on a North Star, others that they used a sun/shadow method. Dr. Smith advised that he tested the sun/shadow method and found that it is possible, in fact, to create a north/south line accurate to within one degree (not as good as the ancient Egyptians!).
Theories put forth related to how the foundation stone was leveled to accept the stones for the pyramid include a water theory which seems difficult to imagine in a country where water is at such a premium. Dr. Smith noted that where the stone courtyard has been quarried away there are curious stone plugs in the bedrock which he believes formed benchmarks that were used for orientation and leveling. The site was rough leveled then a 1-cubit course of stone was put in place to form a platform. This platform was then leveled very precisely. Once the foundation was accurately leveled construction could begin.
A web site – catchpenny.org – contains lots of theories about how the stones for the Great Pyramid were put in place, including aliens, levitation, giant levers, Williamson’s hydraulic theory, cast-in-place concrete, giant kites to raise the stones. He also described work done by a French architect, Jean Pierre Houdin, who has suggested internal ramps. Dr. Smith noted that the ancient Egyptians were very competent engineers who were perfectly capable of devising methods of construction without any help from aliens or magic!
It is possible to move a sledge loaded with a stone block weighing one ton on a flat, prepared surface with just three men. More men are, of course, required if there is a slope that must be negotiated. By constructing ramps in which wooden planks reduced friction, and by lubricating the surface ahead of the sledge, it was a reasonably easy task to move very large loads. Tomb paintings and reliefs on the depict the use of sledges to move such objects as large stone statues. The Egyptians perfected the technique.
William Flinders Petrie measured the Great Pyramid in the 1800s, including the height of each course of masonry. A closer look at the construction of the pyramid reveals that the stones are laid in a pattern of one course of tall stones followed by several courses of smaller stones, then the pattern is repeated. The top half of the pyramid is constructed of stones that are mostly 1 cubit high.. Smith suggested that thelarge courses relate to some of the internal chambers and so probably provided structural support.
Inside the Great Pyramid there are three major chambers. The lower chamber which is in the bedrock beneath the pyramid was never completed. The east side of the chamber is finished but the west is not. Work appears to have been abandoned quite abruptly. . Perhaps an earthquake occurred while work was in progress. The middle chamber, called the Queen’s Chamber, was finished with polished granite walls and roof beams. The grand gallery which leads to the King’s burial chamber has a corbelled ceiling. The King’s chamber’s ceiling is formed by 9 large granite roof beams weighing about 50 tons each. Above the roof of the tomb chamber are five relieving chambers built to support added weight and to transfer the load to the sides.
Herodotus states in his “Histories” that 100,000 workers worked 3 shifts a day for 30 years to build the Great Pyramid. One must remember, however, that Herodotus was writing some 2,000 years after the pyramid was actually built. Dr. Smith developed a work breakdown structure as he would for any large engineering project and then determined the necessary materials and labor related to each task. He estimates that it took a peak workforce of 25,000 to 30,000 people. In all, it required 11 years to complete the construction. Of the total, about 5,000 workers were year-round, permanent employees who lived at the site. Others were drawn from surrounding villages and towns during the inundations when it was impossible to farm.
Based on a request from the National Geographic Society, Dr. Smith developed an estimate of what it would cost to build the Great Pyramid today. He developed two estimates; one using pre-cast concrete blocks, and one using limestone blocks. He also made allowance for OSHA compliance related to ventilation and lighting! He estimated that it would take a workforce of 105 people, and with the benefit of tower cranes, working for 4 years. Construction from pre-cast concrete blocks would cost $1,000.000.000. Construction from limestone blocks would cost $4,000,000,000.
Clearly the building of the Great Pyramid was a public works project of staggering dimensions. The ancient Egyptian were, without a doubt, great engineers with excellent construction and project management skills.