Integrated Geotechnical Evaluation of Subsurface Soil Suitability for Bridge Foundations Using Grain-Size Distribution and Standard Penetration Test (SPT) Data
DOI:
https://doi.org/10.65420/sjphrt.v2i3.182Keywords:
Geotechnical Characterization, Standard Penetration Test (SPT), Direct Shear Strength, Bored Piles, Gypsiferous Soil, Al Zahra'a Intersection, NajafAbstract
This study is a detailed geotechnical investigation of subsurface conditions at Al Zahra'a Bridged Intersection, Najaf Governorate, Iraq. The investigation consisted of 8 boreholes (each 30 m deep) supported by Standard Penetration Tests (SPT), soil sampling and laboratory analyses. The subsurface profile is characterised by medium to very dense clayey silty sand from about 1.0 to 26.5 m, below which is hard silty clay and very dense grey sand. Groundwater was found at shallow depths, about 2.9–3.6 m below ground level. Laboratory data showed a high chemical variability with sulphate, total soluble salts and gypsum values of up to 13.750, 30.100 and 29.564%, respectively. Direct shear tests showed friction angles from 34° to 39° with negligible cohesion. Based on the reported geotechnical conditions, the recommended foundation system was bored reinforced-concrete piles with an approximate diameter of 1.25 m and tip depth of 19 m. The results suggest that foundation design and construction should consider subsurface variability, shallow groundwater and chemical soil properties.
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