Experimental Investigation of Single Model Pile and Pile Group Behavior in Saturated and Unsaturated Sand

The research focus of this paper is directed to investigate the behavior of a single model pile and pile groups in sand under both saturated and unsaturated conditions. Forty different model tests were performed on single piles and pile groups by varying the water-table level. Influence of matric suction, roughness of soil-shaft interface, dilation, and group action were investigated. Test results suggest that the ultimate load-carrying capacity of a single pile and pile groups increased by twofold to 2.5-fold, and settlements decreased significantly due to the matric suction's contribution in comparison with saturated conditions. Erroneous results are likely if conventional soil-mechanics principles are extended in the estimation of pile group capacity and the group efficiency factor for unsaturated cohesionless soils. These errors can be attributed to neglecting the cumulative influence of matric suction and stress overlap in pile group behavior of sandy soils. This study highlights the need for rigorous interpretation of pile load test results taking account of the influence of matric suction when evaluating pile group capacity and group efficiency factor in engineering practice for unsaturated sandy soils. (C) 2019 American Society of Civil Engineers.