GEOTECHNICAL, GEOPHYSICAL INVESTIGATIONS AND SEISMIC RESPONSE ANALYSIS OF THE UNDERGROUND TOMBS IN MUSTAFA KAMIL NECROPOLIS, ALEXANDRIA, EGYPT

The paper presents the geotechnical, geophysical investigations and the numerical static and seismic analysis of selected underground monuments in Alexandria, Egypt i.e. the underground tombs in Mustafa Kamil Necropolis. The analysis of the static stability and the behavior of complex monuments of this kind under seismic loading, are the key factors for the efficient restoration and retrofitting of these underground monumental structures. In the present paper, we present in a first phase a comprehensible geotechnical survey undertaken in this site, comprising geophysical ambient noise measurements (microtremors), as well as field and short – long-term laboratory experiments and tests, in order to define the physical, mechanical and dynamic properties of the soils and soft rock materials. In the second stage, we present the main results of the detailed static and seismic numerical analysis of these underground monumental structures (Catacombs) using the code, PLAXIS b.v with different seismic scenarios corresponding to the seismotectonic features of Alexandria. Advanced soil-rock elastoplastic modeling has been used through out the different phases of the numerical finite element analysis. The aim of the analysis is twofold: (a) to investigate the safety margins of the existing monuments, under their present conditions, against environmental (i.e. weathering) and extreme seismic loads and (b) to investigate the potential improvement of their global behavior applying specific retrofitting techniques.