Subsoil Suitability Evaluation for Deep Foundation Using Geotechnical and Environmental Radioactivity Investigations: Case Study at Cairo, Egypt

This study seeks to assess the foundation beds to evaluate their appropriateness for construction projects using geotechnical and environmental radioactivity investigations. To accomplish this objective, one hundred and three boreholes were sunk to depths varying from 15 m to 40 m below the earth’s surface. The main character of the beds consists of filling material in the first layer, followed by a bed of lean or fat clay or silty sand, and then poorly or well-graded sand. The free swell ratio of fine-grained soil ranges from 23.81% to 90.48%. The clayey soil is classified as low and high plastic soil, determined by the plasticity index. The chemical analysis categorizes the examined samples as non-aggressive soil. The friction angle ranges from 34.9° to 40.7°. The ultimate bearing capacity (Qu) of piles, allowable bearing capacity (Qall), settlement allowable of soil beneath piles, and the bearing capacity of concrete (the pile material) at various diameters (0.8, 1.0, and 1.2) m were computed. Gamma ray spectroscopy was employed to quantify the concentrations of three radioactive elements (thorium, potassium, and uranium) on the ground surface within the research region. The concentrations were evaluated to ascertain the specific radioactivity levels of the radionuclides U, K, and Th, enabling the computation of the annual effective dose rate and the dosage rate. The annual effective dose rate for indoor and outdoor environments ranged from 0.010 mSv/yr to 0.019 mSv/yr and 0.002 mSv/yr to 0.005 mSv/yr, respectively, which are below permissible levels, demonstrating that the research region is free from nuclear hazards. As a future database to reduce possible risks during construction, this study will aid in the area's development and management.