Under seismic excitation, liquefied clean medium to dense cohesionless soils may regain a high le... more Under seismic excitation, liquefied clean medium to dense cohesionless soils may regain a high level of shear resistance at large shear strain excursions. This pattern of response, known as a form of cyclic mobility, has been documented by a large body of laboratory sample tests and centrifuge experiments. A plasticity-based constitutive model is developed with emphasis on simulating the cyclic mobility response mechanism and associated pattern of shear strain accumulation. This constitutive model is incorporated into a two-phase (solid–fluid), fully coupled finite element code. Calibration of the constitutive model is described, based on a unique set of laboratory triaxial tests (monotonic and cyclic) and dynamic centrifuge experiments. In this experimental series, Nevada sand at a relative density of about 40% is employed. The calibration effort focused on reproducing the salient characteristics of dynamic site response as dictated by the cyclic mobility mechanism. Finally, using the calibrated model, a numerical simulation is conducted to highlight the effect of excitation frequency content on post-liquefaction ground deformations.
... 0 It Correlation (Incident waves) Correlation (Reflected waves) , Stressstrain estimatesO OOG... more ... 0 It Correlation (Incident waves) Correlation (Reflected waves) , Stressstrain estimatesO OOGeophysical tests Geophysical test bounds v I ... M. Shakal, A. Processed strong motion records from the CSMIP NSF Treasure Island geotechnical array for the Gilroy earthquake of 16 ...
Journal of Geotechnical and Geoenvironmental Engineering, 2003
Abstract: In saturated clean medium-to-dense cohesionless soils, liquefaction-induced shear defor... more Abstract: In saturated clean medium-to-dense cohesionless soils, liquefaction-induced shear deformation is observed to accumulate in a cycle-by-cycle pattern cyclic mobility. Much of the shear strain accumulation,occurs rapidly during the transition from contraction to dilation near the phase transformation,surface,at a nearly constant low shear stress and effective confining pressure. Such a stress state is difficult to employ as a basis for
Computational simulations are presented for a unique series of centrifuge tests conducted to asse... more Computational simulations are presented for a unique series of centrifuge tests conducted to assess the performance of liquefaction countermeasure techniques. In these centrifuge tests, the dynamic response of an embankment supported on a liquefiable foundation (medium sand) is investigated. The experimental series included: (i) a benchmark test without a liquefaction countermeasure, (ii) foundation densification below the embankment toe, and (iii) use of a sheet-pile containment enclosure below the embankment. This series of experiments documents a wide range of practical liquefaction response mechanisms (including countermeasure implementation). In order to numerically simulate the above centrifuge tests, a new calibrated soil stress-strain constitutive model is incorporated into a two-phase (solid-fluid) fully coupled Finite Element formulation. Comparison of the computational and experimental results demonstrates: (i) importance of post-liquefaction dilative soil behavior in dictating the dynamic response and deformation characteristics of the embankment-foundation system, and (ii) capabilities and limitations of the numerical modeling procedure.
Under seismic excitation, liquefied clean medium to dense cohesionless soils may regain a high le... more Under seismic excitation, liquefied clean medium to dense cohesionless soils may regain a high level of shear resistance at large shear strain excursions. This pattern of response, known as a form of cyclic mobility, has been documented by a large body of laboratory sample tests and centrifuge experiments. A plasticity-based constitutive model is developed with emphasis on simulating the cyclic mobility response mechanism and associated pattern of shear strain accumulation. This constitutive model is incorporated into a two-phase (solid–fluid), fully coupled finite element code. Calibration of the constitutive model is described, based on a unique set of laboratory triaxial tests (monotonic and cyclic) and dynamic centrifuge experiments. In this experimental series, Nevada sand at a relative density of about 40% is employed. The calibration effort focused on reproducing the salient characteristics of dynamic site response as dictated by the cyclic mobility mechanism. Finally, using the calibrated model, a numerical simulation is conducted to highlight the effect of excitation frequency content on post-liquefaction ground deformations.
... 0 It Correlation (Incident waves) Correlation (Reflected waves) , Stressstrain estimatesO OOG... more ... 0 It Correlation (Incident waves) Correlation (Reflected waves) , Stressstrain estimatesO OOGeophysical tests Geophysical test bounds v I ... M. Shakal, A. Processed strong motion records from the CSMIP NSF Treasure Island geotechnical array for the Gilroy earthquake of 16 ...
Journal of Geotechnical and Geoenvironmental Engineering, 2003
Abstract: In saturated clean medium-to-dense cohesionless soils, liquefaction-induced shear defor... more Abstract: In saturated clean medium-to-dense cohesionless soils, liquefaction-induced shear deformation is observed to accumulate in a cycle-by-cycle pattern cyclic mobility. Much of the shear strain accumulation,occurs rapidly during the transition from contraction to dilation near the phase transformation,surface,at a nearly constant low shear stress and effective confining pressure. Such a stress state is difficult to employ as a basis for
Computational simulations are presented for a unique series of centrifuge tests conducted to asse... more Computational simulations are presented for a unique series of centrifuge tests conducted to assess the performance of liquefaction countermeasure techniques. In these centrifuge tests, the dynamic response of an embankment supported on a liquefiable foundation (medium sand) is investigated. The experimental series included: (i) a benchmark test without a liquefaction countermeasure, (ii) foundation densification below the embankment toe, and (iii) use of a sheet-pile containment enclosure below the embankment. This series of experiments documents a wide range of practical liquefaction response mechanisms (including countermeasure implementation). In order to numerically simulate the above centrifuge tests, a new calibrated soil stress-strain constitutive model is incorporated into a two-phase (solid-fluid) fully coupled Finite Element formulation. Comparison of the computational and experimental results demonstrates: (i) importance of post-liquefaction dilative soil behavior in dictating the dynamic response and deformation characteristics of the embankment-foundation system, and (ii) capabilities and limitations of the numerical modeling procedure.
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