Integration of geophysical techniques to detect geotechnical hazards: a case study in Mokattam, Cairo, Egypt

Geotechnical hazards are the main factors that control decisions about construction in structurally complex zones. In the Mokattam area, Cairo, Egypt, different techniques, such as geotechnical techniques, remote sensing, and geophysical tools, are used and integrated to study the subsurface lithology, caves and structures to evaluate the possible geotechnical problems in these zones for expected future development in this area. Remote sensing applications indicate that the main trends of surface lineaments are E-W to NW-SE, whereas the minor trends are N-S to NE-SW. Ten vertical electrical sounding stations (VESs) were acquired and interpreted to delineate the subsurface stratigraphy. The interpretation results of these data show that the subsurface stratigraphy consists of 6 geoelectric units arranged from the surface to the bottom: fractured limestone, clay, marly limestone, dolomitic limestone, marl and marly limestone, and limestone. Nine electrical resistivity tomography (ERT) profiles, twelve shallow seismic refraction (SSR) profiles, and ten ground-penetrating radar (GPR) profiles were acquired to study the shallow subsurface stratigraphy. The integration results of ERT and SSR measurements indicate that the shallow subsurface stratigraphy is composed of different rock units. The first layer is fractured limestone, which represents the surface layer of the upper plateau and contains caves in some areas. Then, layers of clay and marl, which are important geotechnical hazard sources, are present. Finally, a layer of limestone appears in the bottoms of some sections, and this limestone layer also contains caves. The GPR profiles have the highest resolution and can discriminate the top horizon into three to four detailed stratigraphic units, each of which has different amplitude values and caves and fractures in some profiles.

Automated summary

In the Mokattam area in Cairo, Egypt, various techniques such as geotechnical techniques, remote sensing, and geophysical tools are used to study the subsurface lithology, caves, and structures to evaluate potential geotechnical problems for future development. Remote sensing shows main trends of surface lineaments are E-W to NW-SE, while the minor trends are N-S to NE-SW. The subsurface stratigraphy consists of fractured limestone, clay, marly limestone, dolomitic limestone, marl and marly limestone, and limestone from the surface to the bottom.