Geotechnical and environmental radioactivity investigations at Al Sādis Min Uktōber city, Cairo municipality (Egypt), for the high-speed railway construction

The present study aims to evaluate the possibility of constructing a new high-speed railway (HSR) at Al Sādis Min Uktōber city, Cairo (Egypt): geotechnical and environmental radiological hazards are estimated from several collected soil and water samples. A variety of laboratory geotechnical tests such as grain size, free swelling test, liquid and plastic limits, chemical analysis and uniaxial compression strength are applied to sixty-one drill holes. A geotechnical examination of the coarse-grained soil at the foundation level classified it as poorly graded soil. The results of the investigation of fine-grained soil at the foundation level shown that the liquid limit ranges from 22% to 55%, the plastic limit ranges from 12% to 28%, the plasticity index varies from 11% to 33%, free swelling varies from 51% to 71%. Mechanically, the uniaxial compressive strength values on rock samples range from 6.96 MPa to 142.39 MPa. The radioactive study is performed to detect the ²²⁶Ra, ²³²Th, and ⁴⁰ K activity concentrations of the soil samples: their mean values are 34 ± 10 Bq·kg^-1, 14 ± 5 Bq·kg^-1 and 552 ± 20 Bq·kg^-1, respectively. The values of radiological hazard indexes are not exceeded the permissible limits: e.g. the mean value of absorbed dose rate is 47 ± 6 nGy h^-1; the annual gonadal dose equivalent is 0.3 ± 0.04 mSv·y^-1; the lifetime cancer risk is 02 ± 0.2·10^-3. Thus, the soil in the studied railway area is safe to use in building materials and infrastructure applications: the radiological hazards and the geotechnical studies confirmed the studied area is suitable to construct a new community having a HSR. According to the SWOT-PEST and environmental impact analyses, the construction of the HSR meets the criteria of the Kyoto Protocol, the EU Climate and Energy policy, and other international treaties.