Geotechnical Evaluation of the October- Abu Roash Urban Bedrocks Based on Lithomorphic Analysis of the Volcanic/Clastics Outcrops, Greater Cairo, Egypt

Abstract

The October Abu Rawash corridor represents one of the most significant zones of urban expansion in Greater Cairo, having undergone substantial transformation in recent decades due to rapid population growth and associated development pressures. However, this growth has been accompanied by notable geotechnical challenges, primarily stemming from the area's complex and heterogeneous subsurface conditions. The foundation problems are largely attributed to the juxtaposition of clastic soils with highly weathered volcaniclastic bedrock, characterized by abrupt lateral and vertical lithological variations and a dense, multidirectional fracture network. These geological features significantly increase the risk of differential settlement. In addition, the widespread presence of expansive clay minerals both within the volcaniclastic units and the argillaceous Qatrani Sandstone further compromises the mechanical stability of the foundation soils by reducing their bearing capacity and increasing susceptibility to volumetric changes with moisture fluctuations. The region is also exposed to multiple geo-environmental hazards, including slope instability along the main escarpment and rising groundwater levels in the adjacent cultivated urban zones. These hazards are exacerbated by inadequate drainage infrastructure, aging water distribution systems, and seepage effects, particularly in areas underlain by clay-rich volcanic and clastic formations. Moreover, predicted climate change impacts and unsustainable land-use practices may further intensify the associated risks. To address these challenges, a comprehensive geological and geotechnical risk assessment was conducted, incorporating geomorphological, lithological, petrographical, mineralogical, and geoengineering parameters. Based on the integrated analysis, the study proposes a set of targeted management strategies and geotechnical recommendations aimed at enhancing ground stability and supporting future urban development in the area.