Abstract The Catacombs of Kom el-Shoqafa in Alexandria, known as Treasure Hill, serve as a remarkable burial site and royal tomb dating back to the 2nd century AD. This archaeological site has been recognized as one of the Seven Wonders of the Medieval World. Throughout history, these catacombs have suffered from the effects of flash floods and seismic activity. As a result, they have experienced various degrees of damage and instability, which have worsened over time. It is well-documented that rising groundwater levels within the Catacombs, triggered by heavy rain or seawater intrusion, can significantly affect the seismic behavior of this historic underground structure. Furthermore, the presence of this groundwater alters the characteristics of earthquake motions, leading to considerable amplification and variability in seismic activity. This study employs geotechnical modeling and examines stress and deformation using the advanced PLAXIS software. Numerical simulations were carried out to investigate how flash floods and rising seawater levels, exacerbated by climate change, influence the seismic resilience of monumental underground edifices. The research identifies critical factors affecting seismic stability, deformation, and failure mechanisms, while highlighting areas of concern, and evaluating the present status of tomb stability. The results indicate that during significant earthquakes with a Peak Ground Acceleration (PGA) above 0.24 g, the presence of groundwater tends to amplify the horizontal acceleration response across the upper, middle, and lower sections of the Catacombs, as well as impact the main load-bearing columns and piers situated on the second and third tiers. It was also observed that both horizontal and vertical displacement responses are greatly increased due to the severe seismic compressive and shear stresses that accompany substantial groundwater inundation of these subterranean structures. For minor earthquakes, specifically those with a PGA below 0.16 g, the effects of groundwater on the tomb responses are virtually insignificant. Thus, the influence of groundwater on the seismic behavior of underground structures becomes increasingly evident during larger earthquakes compared to smaller ones. In scenarios with elevated groundwater levels, co-seismic deformation is more pronounced. These findings provide crucial recommendations for future reinforcement and retrofitting initiatives and act as a valuable reference for assessing the stability of other complex underground structures worldwide.
Sayed Hemeda (Wed,) studied this question.
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