Geotechnical Assessment and Soil Improvement of Al-Hilla Gas Station Site, Babylon, Iraq

Abstract

    This paper studies the geotechnical properties of the soil at Al-Hilla Gas Station, based on investigations conducted in 2024. The study included digging four boreholes to a depth of 15 m. The evaluation was based on fieldwork and laboratory test results for both disturbed and undisturbed soil samples taken from the study site. The results showed that the type of soil is silty clay containing a small percentage of sand up to a depth of 6.5 m and is classified as highly plastic clay and low plasticity. Beyond a depth of 6.5 -15 m, the soil is classified as medium to high density sandy silt. A chemical analysis results indicated that the groundwater is slightly basic, while the salts content ranged from medium to high. The water also contained a high percentage of sulphates. The organic matter content ranged between 0.54-5.77%, the total soluble salts between 9.14-17.21%, and the gypsum content between 5.87-10.43%. The average number of hits (N) for standard penetration test (SPT) was between 9-43, the groundwater level was 3.90 m, and the moisture content (MC) ranged between 9.1-28.4%. The liquid limit (L.L.) ranged from 36-51%, the plastic limit (P.L) from 18-21%, and the plasticity index (PI) from 20-33%. The average soil effectiveness value was around 0.50, classifying the soil as inactive. The soil bearing capacity ranged between 2.16-2.56 tons. For the dynamic method, the bearing capacity ranged between 5.15-5.24 tons/m2. Several engineering treatments can be used depending on type of soil, groundwater level, and type of structure. Based on the results, this study recommends that the best type of treatment is soil replacement, by removed surface layers and replaced with gravel or clean, compacted sand.