Measured soil–structure interaction for concrete piles subjected to lateral loading

Lateral loads often control the design of deep foundations. This paper focuses on improving the understanding of soil–structure interaction (SSI) of laterally loaded piles and developing p–y curves based on simultaneous direct measurements of the soil–pile interaction pressure (p) and lateral pile displacement (y) along the length of the pile. This paper summarizes the methodology, instrumentation, soil–pile interaction measurements, and procedure used to investigate the soil–pile interaction and to develop the directly measured p–y curves. A 102 mm diameter, 1.42 m long precast concrete pile was fully instrumented with advanced sensors and installed in well-graded sand. The digital image correlation (DIC) data indicated that the soil movement in front of the pile extended up to 6.3 pile diameters (6.3D) from the pile center. The normalized measured maximum soil–pile interaction pressures closely matched the normalized pressures provided in the literature for short, stiff laterally loaded piles installed in cohesionless soils. In addition, the direct measurement-based p–y curves at different depths showed nonlinear behavior, in which the initial stiffness and ultimate soil reaction increased as the depth increased. When compared to p–y curves calculated from measured strain along the pile length, the directly measured p–y curves showed differences of ultimate soil reaction ranging from 8% to 33%. When compared to p–y curves calculated using the procedures available in the literature, the measurement-based p–y curve ultimate soil reactions have differences ranging from 5% to 189%. The differences in ultimate soil reaction could be mainly attributed to the installation method.