Seismic response of pile group embedded in unsaturated soil considering the coupling of kinematic and inertia pile-pile interactions

Both inertia and kinematic pile-soil-pile interaction should be considered during the seismic response analysis of a pile group. This study established a novel mathematical framework which is capable of considering the coupling of inertia and kinematic interactions, the complex constitutive of unsaturated soil, and the secondary wave effect within a pile group. By comparisons with existing analytical and numerical answers, the validity and advancement of the proposed model is exhibited. The main findings can be summarized as: (1) Simplified soil constitutive models, such as the BDWF model and the saturated soil model, would fail to reveal the authentic response of pile group. The saturation and porosity would significantly influence the kinematic pile-pile response factor, while the inertia pile-pile response factor is less influenced; (2) increases of pile numbers within a pile group would impose severe fluctuations on the kinematic response of the pile group, whereas the increase of pile spacing would significantly diminish this effect; (3) secondary wave effect should never be overlooked in seismic analysis but can be neglected in inertia analysis.