Influence of Ground Improvement on liquefaction Induced Settlement Observations from Case Histories and Centrifuge Experiments

다국어 초록 (Multilingual Abstract)

Over 100 case histories for sites with ground improvement has been compiled in order to provide an overview of the actual field performance of improved sites under strong seismic loading. The data show that improved sites generally performed well. Improved ground sites experience less deformation than their unimproved neighbors. Unacceptable performance, when it occurs, can be explained most commonly by excessive ground displacements due to laterally flowing soils or inadequate remediation zone depth or lateral extent. The case history data is supported by results of dynamic centrifuge experiments which show that for low levels of shaking, typically 0.2 g or less, the amount of settlement of the foundation element decreases with increasing improved zone depth. Moreover, the amount of differential settlement of the foundation decreases significantly with increasing level of ground improvement. For high levels of shaking (peak ground acceleration in excess of 0.7 g) and very loose soil the settlements are significantly greater for all depths of improvement. The experimental results also show that leaving a thin layer of unimproved soil below a thick improved zone can lead to large concentrations of strains and liquefaction and produce excessive settlements.