| One objective of this centrifuge study was to investigate the effect of seismically-induced permanent lateral ground displacement of a multi-layer soil profile on end-bearing and floating pile group foundations. A proposed retrofitting/rehabilitation method was also studied. The method could be applied locally both during and after construction, and could be utilized with existing foundation systems. The study also investigated the effects of superstructure inertia on pile group models with and without the presence of the proposed pile retrofitting.; Another objective of this study was to investigate the effectiveness of a new ground improvement technology, a passive site remediation methodology, for liquefaction mitigation. Centrifuge tests were conducted to investigate the behavior of a loose soil deposit that was treated with a colloidal silica solution. Various grouting/saturation techniques were tried to achieve a well-grouted soil formation. Lateral spreading, settlement, and liquefaction responses of the treated sand were measured under various earthquake motions, and then compared with those measured from the untreated soil deposits. This passive site remediation concept was then implemented on model pile groups to reduce the adverse effects induced by liquefaction and lateral spreading.; The results indicated that the proposed pile retrofitting method, as well as the passive site remediation utilizing a colloidal silica solution, significantly reduced bending moments and the axial forces imposed on the piles during lateral spreading. Colloidal silica treated sand showed significant resistance against liquefaction while reducing deformations, and the treated sand performed adequately under repeated earthquake motions. Passive site remediation methodology utilizing colloidal silica stabilizer can be an alternative remediation technique to traditional ground improvement methods for existing foundation systems placed in liquefiable soils. |
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