The Effect of Mineralogy on the Geotechnical Properties of Clayey Soils: A Case Study for Al-Qurna District, Basrah, Iraq

This study investigates the influence of mineralogical composition on the geotechnical properties of clayey soils in the Al-Qurna District, Basrah, Iraq. The research focuses on understanding these soils' swelling potential and classification through laboratory analyses, including Atterberg limits, grain size distribution, X-ray Diffraction, and Scanning Electron Microscopy. Results indicate that the soils are dominated by montmorillonite (31.5%), which is the most significant swelling clay mineral, followed by kaolinite (13.16%) and illite (13.56%), with non-clay minerals such as calcite (52.05%) and quartz (31.52%) also contributing significantly. The grain size analysis classifies the soils as silty clay, with silt (60.2%), clay (33.1%), and sand (6.2%). The Plasticity Index (PI) ranges between 12% and 37%, classifying the soils into low to high-plasticity clays (CL and CH) and silts (ML) according to the Unified Soil Classification System. While the overall swelling potential is evaluated as medium, specific layers with higher montmorillonite content and PI values exhibit increased susceptibility to expansion under moisture variations. The role of calcium in stabilizing the soil and mitigating swelling potential is also highlighted. The findings emphasize the importance of understanding soils' mineralogical and textural properties for geotechnical applications. Appropriate mitigation measures, such as soil stabilization and improved drainage, are recommended for regions with high swelling potential to ensure the structural stability of engineered systems.