<p>Existing design guidelines for considering the kinematic and inertial effects on piles and their combination in seismic design of piles in liquefaction-induced lateral spreading ground provide conflicting recommendations, partly because experimental data on the phase relationship between the kinematic load and the inertial load on piles is limited. In this study, a centrifuge shaking table test was conducted on single piles embedded in a half sloping liquefiable ground. Two single piles with and without superstructure mass at pile heads were used to represent pile foundations with different loading combinations. The pile with a superstructure was used to simulate the seismic response under the combined effects of kinematic and inertial loads, while the pile without a superstructure simulated the response dominated by kinematic loads. The soil model consisted of a clay crust overlying a saturated loose sand layer, which was underlain by a saturated dense sand layer. The results showed that the depth of the maximum bending moment of the pile with a superstructure was shallower than that of the pile without a superstructure. The bending moment response of piles may be predominantly governed by inertial loads, even when the kinematic load was substantial. For the pile with a superstructure, the kinematic and inertial loads were out-of-phase, whereas for the pile without a superstructure with negligible inertial effect, the two loads were in-phase. The kinematic and inertial loads were out-of-phase when the natural period of pile was greater than that of the ground; otherwise, the two loads acted in-phase.</p>