Centrifuge study of high-rise pile cap foundations under lateral cyclic loading in clay and sand

This study investigates the behavior of HPCFs under lateral monotonic and cyclic loading using geotechnical centrifuge tests. Two foundation conditions were considered: silty clay and sand. Multi-stage cyclic loading tests were performed with load amplitude ratios ζb ranging from 0.2 to 0.7 and up to 2000 cycles per stage. The evolution of foundation displacement, excess pore water pressure (EPWP), and tilt angle was analyzed. The results show that lateral bearing capacity of the HPCF in silty clay is approximately half that of sand. Cumulative displacement is governed primarily by ζb; when ζb > 0.5, displacement increases significantly with cycle number N. A “self#healing” response is observed when ζb is reduced from 0.7 to 0.2. In silty clay, the tilt angle evolves step#wise owing to cyclic damage accumulation, whereas it exhibits a progressive increase in sand. The EPWP ratio ri increases with ζb but may stabilize or decrease with N, peaking at the front pile due to uneven load distribution in the pile group. Using a power#law fitting method, the foundation tilt after 107 cycles is predicted. For silty clay, the predicted tilt is substantially larger than that of dense sand for the same ζb value.