Evaluating the liquefaction potential of soils by the energy method in the centrifuge.

摘要

Liquefaction of saturated sands during earthquakes has been a major cause of damage to buildings and earth embankments. The energy method for the analysis of densification and liquefaction of cohesionless soils is based on the fact that during deformation of these soils under dynamic loads, part of the energy is dissipated into the soil.; This study deals with the validation of this procedure through centrifuge testing. To use the new geotechnical centrifuge facility at Case Western Reserve University (CWRU) in studying liquefaction of soils, required the development of a feedback correction procedure for the shake table input signals and an appropriate procedure for model preparation, as well as the design of a saturation system setup. An effective procedure for shake table control has been developed. The CWRU laminar box for geotechnical earthquake centrifuge simulations has been successfully constructed and tested.; Centrifuge liquefaction testing of several soils with different grain-size characteristics made it possible to evaluate the validity of the energy method in determining the liquefaction potential of a soil deposit. A total of 30 dynamic centrifuge tests at a scale of N g's were conducted on scaled pore fluid-saturated models. The influence of relative density and effective confining pressure as well as the effect of different grain size distribution on the energy per unit volume required for liquefaction is studied. This study presents a simplified procedure for reconstructing the shear stress strain history to liquefaction at different depths, within the prototype, as well as for calculating the energy per unit volume from the recorded horizontal accelerations and lateral displacements of the laminar box segments. Generalized relationships were obtained by performing regression analyses between the energy per unit volume at the onset of liquefaction and liquefaction affecting parameters.; A rational procedure to decide whether or not liquefaction is imminent can then be formulated by comparing the calculated unit energy from the time series record of a design earthquake with the resistance to liquefaction in terms of energy, based on in situ soil properties.