Evaluation for Ultimate Horizontal Load Capacity and Subsurface Hinge Depth in Sand-RC Pile Foundation Systems

This study verified the accuracy of a simplified estimation method for the ultimate horizontal load capacity of soil-RC pile foundation interaction systems by comparing it with a numerical model that simulates nonlinear behavior of the ground and pile members. The analysis considered various pile diameters (0.5 m, 1.0 m, 1.5 m, 2.0 m) and ground relative densities (30%, 60%, 90%). In the model, the pile bottom was fixed, and the head was constrained to rotation only. A pushover analysis was performed until the pile exhibited a two-hinge bending failure. Comparison with Broms’s evaluation method revealed that the ratio of the numerical analysis results to the simplified estimates increased as pile diameter decreased and ground density increased. For smaller pile diameters (0.5 m and 1.0 m), the ratio ranged from 1.0 to 1.5, whereas for larger diameters (1.5 m and 2.0 m), it ranged from 0.9 to 1.2. Furthermore, when the relative density of the soil was 30%, the simplified estimation results significantly underestimated the ultimate horizontal capacity compared to the numerical results.