Near-Surface Assessment in East Cairo using Shallow Seismic Refraction and Geotechnical Methods for Foundation Hazard Evaluation

Urban expansion into desert environments presents unique geotechnical challenges that require detailed subsurface characterization to ensure safe and sustainable development. This study presents a comprehensive subsurface assessment of East Cairo using seismic exploration and geotechnical test data to evaluate subsurface risks and stability. Seismic imaging delineated four geoseismic units: sand and clay with rock fragments, sandstone, shale, and fractured limestone. The primary subsurface hazards identified in the study area are shale layers and fractured limestone zones. These challenges highlight the need for detailed geotechnical studies to support safe design. Geotechnical studies revealed variable subsurface conditions affecting soil strength and stability. Moisture content and Atterberg limits showed high plasticity and sensitivity to water, suggesting potential for volumetric changes and deformation under environmental fluctuations. Unconfined compressive strength (UCS) and Rock Quality Designation (RQD) results indicated weak to moderately competent materials, with several zones exhibiting poor structural integrity and fractured profiles. Shear strength parameters, including cohesion and internal friction angle, varied widely, pointing to inconsistent resistance to slope failure and lateral loads. Particle size distribution confirmed the presence of well-graded soils in some areas, while others retained excessive fines, increasing moisture retention and swelling behavior. Our results provide a critical decision-making framework for foundation design and risk mitigation, demonstrating the necessity of an integrated subsurface assessment for urban development in complex geological settings, justifying the need for targeted engineering solutions, and informing the functional classification of the site into zones of varying geotechnical risk.