Preservation of Heritage Buildings Against Natural Processes: The Case of the Saint George Church (Old Cairo, Egypt)

Abstract

The Saint George church (Old Cairo, Egypt) is a unique masonry building complex comprising structures of different time periods (Pharaonic, Medieval, Roman periods, 1909 construction, 1909–1930 modifications, 1941 reconstruction). The area has been affected by floods before the construction of Aswan High Dam and high groundwater level of Nile River resulting in loading and unloading of soils and ground settlements. Moreover, the high groundwater level flooded the lower floor levels of the structure. The building complex is founded on native dense alluvial sands, silts and clayey soils, during the low water periods of river flow. Parts of the temple are founded on shallow depth, while its inner part is built on remnants of a Roman tower, which is founded on deeper soils. The church was at moderate risk to damage from extensive construction vibrations, differential settlements from groundwater lowering or earthquakes. Taking into account the aforementioned, the geological, geotechnical and hydrogeological conditions of its site were studied and church failures comprising mainly cracks were mapped and attributed to the construction complexity of the building and to differential settlements induced by groundwater level fluctuations. Based on the results of this study, lowering of the water table as part of a greater dewatering project was proposed and expected settlements were calculated. After terminating groundwater lowering, differential settlements were measured confirming the abovementioned calculations. For further protection and preservation of the monument, the maintenance of the groundwater level below the oldest foundations along with the installation of crack monitoring systems were proposed.