The Great Pyramid of Giza, built for Pharaoh Khufu, has stood for approximately 4,600 years. Many other ancient Egyptian structures have significantly deteriorated over this vast timescale. Despite enduring strong seismic activity and the gradual loss of its smooth white casing stones, the pyramid’s core structure remains largely intact, with its granite and limestone blocks still in place.
For a long time, archaeologists and other experts have been trying to decipher the engineering principles that enabled the pyramid to survive for millennia. It holds the unique distinction of being the sole surviving wonder from the Seven Wonders of the Ancient World. A recent study, published in the journal Scientific Reports, offers an additional plausible explanation for its remarkable durability.
The focus of this new research is on the empty relieving chambers situated directly above the pharaoh’s burial chamber. According to the researchers, these voids might have contributed to the structure’s stability against earthquakes, even if this was not an intentional design goal of the ancient builders.
The Great Pyramid represented an immense construction undertaking, involving approximately 2.3 million stone blocks with a combined weight of around 66 million tons. Some of these blocks were transported to the construction site from hundreds of kilometers away. They were then meticulously positioned, creating a primarily solid edifice reaching a height of about 147 meters, with only a few internal chambers.
This inherent form contributes significantly to the pyramid’s robustness. The majority of its weight is concentrated at the base and is evenly distributed across a wide foundation. However, specialists believe this alone is insufficient to fully protect the structure from the ravages of time and seismic disturbances. Evidence of this can be seen in other pyramids that have fared far worse; for instance, the outer structure of the Meidum pyramid partially collapsed in antiquity, and the pyramids of Userkaf, Sahure, and Unas now resemble mere piles of rubble.
Similar vulnerabilities to shear forces during earthquakes have been observed in stone pyramids in Mesoamerica. While Egypt is not considered a highly seismically active region, significant tremors have occurred near the Great Pyramid. Planet Today reports that at least two major earthquakes have been recorded within an 80 km radius. An earthquake with a magnitude of approximately 6.8 struck the area in 1847, followed by a 5.8 magnitude earthquake in 1992. These events resulted in the detachment of a few casing stones from the upper portion of the Giza pyramid.
To investigate the reasons behind this structure’s extraordinary longevity, a team led by seismologist Asem Salama from Egypt’s National Research Institute of Astronomy and Geophysics installed vibration sensors both inside and around the pyramid. The scientists aimed to understand how the pyramid responds to environmental movements.
A total of 37 portable accelerometers were strategically placed at various locations. These instruments were positioned in the King’s Chamber, the Queen’s Chamber, within the vertical relieving chambers above the King’s Chamber, in passageways and tunnels, on the exterior stones, and on the surrounding ground. These devices were capable of detecting even very faint vibrations, continuously generated by factors such as distant traffic, wind, the passage of oceanic wave energy through the Earth, and subtle crustal movements.
The analysis revealed that the dominant background frequency in the ground surrounding the pyramid was approximately 0.6 Hz. In contrast, most areas within the pyramid itself exhibited frequencies ranging from about 2.0 to 2.6 Hz. This discrepancy suggests that seismic energy is not transferred very efficiently from the ground to the structure. In essence, this prevents resonant amplification, a phenomenon that frequently leads to severe structural damage in buildings.
Overall, vibrations were distributed fairly uniformly throughout the pyramid, with amplification increasing towards the upper sections. However, the relieving chambers stood out prominently from this pattern. It was within these cavities that the amplification of vibrations notably decreased. While these chambers are typically understood as a means of reducing the load on the King’s Chamber, the new findings indicate they may have also played a role in redistributing internal stresses and interrupting the propagation of vibrations.
The researchers emphasize that it is premature to definitively conclude that earthquake protection was an intentional design feature of the pyramid. At this stage, such conclusions remain hypothetical. Nevertheless, the authors suggest that the data obtained indicates that the ancient Egyptian builders possessed a profound understanding of soil dynamics and structural principles.
The scientists plan to conduct further measurements in key locations where minor deviations were observed. They anticipate that this new data will enable a more precise assessment of the role played by internal voids and confirm that the Great Pyramid is not only a remarkable architectural achievement but also a testament to ancient construction techniques capable of withstanding seismic loads.
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