Engineering Site Investigation inside Basrah City, Southern Iraq using Cross-hole Seismic Refraction Technique (A Case Study)

Abstract

This project includes cross-borehole seismic survey to determine the compressional and shear wave velocities, elastic moduli, and geotechnical properties of the soil at a hospital’s site inside Basrah City, Southern part of Iraq to evaluate the required properties of the soil to design a safe foundation for the construction purposes. Five boreholes were drilled in the study area; two of them were to generate waves and the other three boreholes to receive the waves. Standard Penetration Test in borehole 4 showed the existence of weak soft soil at a 10 to 15 m depth. All boreholes from depths 1-15 m were injected with cement and quick-hardening materials to enhance the consistency of the soil. A few days after injection, compressional and shear wave velocities, and the strength of the soil were increased according to this operation and then after, it was considered as stiff (competent) soil. Ultimate bearing capacity values were found between 12.36 and 14 T/m², which reflect stiff consistency, especially from a depth 1 to 10 meter. However, it indicated that the soil site was capable of bearing light and medium weights. Based on these results, the cover layer is considered a soft filling material with a thickness of 1 m. The soil was divided into four layers; the first one is stiff to very stiff sand silty clay (2 to 3) m in depth, the second layer is medium to stiff at 3 to 6 m depth, the third layer is stiff (6 to 9) m depth, and the fourth layer is soft silty clay at 9 to 15m depth.