Behavior of a Pile Group Supporting a Precast Pile Cap under Combined Vertical and Lateral Loads

A half-scale field test was conducted on a pile group installed at a stiff clay site. The pile group consisted of eight steel H-piles, with a battered pile at each corner, and connected to a precast pile cap using preformed socket connections. The pile foundation system was tested under different combinations of vertical and lateral loads. The magnitude of the loads, as well as the height of the lateral loads, were varied to produce different overturning moment-to-lateral load ratios. These load combinations enabled the researchers to investigate the foundation system for both nonseismic and seismic conditions as well as its behavior under extreme loading. The pile group produced excellent resistance during different phases of testing although there were differences in the behavior of battered and vertical piles. Under simulated seismic loading, the battered piles sustained 17% more axial compression forces, 100% more axial tension forces, and 33% lower bending moments than the vertical piles. A numerical model developed to investigate the pile behavior produced a good agreement between the measured and computed pile responses.