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This study investigates the influence of slope position, soaking, and leaching on the geotechnical properties of soils from a sloping site in Annajaf city, Iraq, integrating field Plate Load Tests (PLT) and laboratory analyses. Soil samples from the…
This study investigates the influence of slope position, soaking, and leaching on the geotechnical properties of soils from a sloping site in Annajaf city, Iraq, integrating field Plate Load Tests (PLT) and laboratory analyses. Soil samples from the slope top (compacted, poorly-graded silty sand, SP-SM) and bottom (natural, silty sand, SM with higher fines, gypsum, and organics) were characterized. PLTs were conducted under natural and soaked conditions at varying distances (X = 5m, 10m) from the crests of two slopes (θ = 37°, 41°), where X is the horizontal distance from the slope crest to the center of the test plate. Laboratory tests included Standard Proctor compaction and direct shear tests on natural, soaked, and leached specimens prepared to field density. Results indicate soaking dramatically reduced the modulus of subgrade reaction (k) derived from PLTs by 6-27% related to the slope geometry and the laboratory-measured friction angle (Φ) by 35-43%. Leaching altered compaction parameters (MDD, OMC) and shear strength, influenced by initial soil composition. Steeper slopes and proximity to the crest further decreased soil stiffness (k). While compaction mitigated the weakening effect of saturation on the slope top compared to the natural bottom soil, significant reductions in k and Φ still occurred. The findings highlight the necessity of considering slope geometry, position, potential saturation, and leaching effects, using combined field and laboratory data for robust geotechnical design on slopes.
