DETERMINING CAUSES OF STRUCTURAL BUILDING DAMAGES IN 15TH OF MAY CITY, CAIRO, EGYPT, USING GEOPHYSICAL AND GEOTECHNICAL APPLICATIONS

The 15th of May City is a suburb in the south of Cairo that developed over the last 25 years. The city is built on Eocene sedimentary rocks of mainly limestone. Despite its young age, the city has many buildings with severe structural damage, which mainly developed over the last 10 years. The reasons for the structural damage were unknown and led to this study. Both geophysical and geotechnical investigations were carried out in order to determine these causes. Four geoelectric profiles with dipole-dipole arrays have been carried out. The results of these geoelectric investigations identified the existence of different geoelectric zones with different resistivities in the subsurface. The lowest resistivity in the geoelectric zone reveals shale deposits intercalated with limestone rocks while the high resistivity reveals only limestone bedrock. Scanning electron microscopy (SEM) analysis of the Eocene shale shows pores and micro-cracks with thin films of salts, mainly halite, covering the carbonate and clay minerals. As a result, the interaction of clay minerals and salts with groundwater seepage, most likely is the geo-technical problem causing the
cracking of the buildings in the 15P
th
P of May City. It is strongly recommend that geophysical and geotechnical
investigations should be taken into account before any further constructions at the new suburbs.