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EVALUATION OF PULL-OUT CAPACITIES OF DIFFERENT PILE MODELS EMBEDDED IN UNSATURATED SANDY SOIL

The rises of capillary water above the water table level in soil layers and make the soil partially saturated that is considered one of the most challenging problems that a geotechnical engineer may encounter. Partially saturated soils contain large percentages of voids between the structural soil particles that are filled by water instead of air. Physical and mechanical properties of partially saturated soils are different than the other soils (i.e. dry or saturated) such as effective stress, shear strength and seepage. In present work, pile models manufactured from steel with different geometry (H-pile, hallow square pile, and closed-ended pipe pile) of the same surface area embedded in partially saturated sand soils to investigate the uplift capacity. Poorly graded fine sand obtained from Baghdad city was used throughout this research. Partially saturated soils were obtained by lowering water level below soil surface to a depth of (i.e. 150 and 450 mm). Test results showed from the suction profiles of the soil that the matric suction increases with the lowering of water table. The ultimate uplift pile capacity was different in values based on the matric suction values. A comparison was made between the behaviors of steel pipe pile with other shapes of pile models used in terms of uplift capacities. The results showed that the degree of improvement in values of uplift capacity for first lowering of water level 150mm were (2.36, and 1.11) times than that of H-pile, and square piles, respectively. While the improvement in uplift capacity for a pipe pile when the water table level was lowering to a depth of 450mm, were greater than those of H-pile, and square steel piles by (2.22, and 1.10), respectively.