Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher.
Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?
Some links on this page may take you to non-federal websites. Their policies may differ from this site.
-
Cyclic direct simple shear tests were conducted to study the liquefaction-induced permanent deformations caused by non-uniform shear stress waves which mimic the acceleration time histories used in the LEAP centrifuge experiments. The experiments reported here were used as the basis for evaluation of a number of leading constitutive models for sands during LEAP-2020 type-A prediction exercise. The dataset may be used in the assessment of the performance of current and future constitutive models for sands.more » « less
-
Cyclic response of Ottawa F65 Sand was investigated in constant-volume Direct Simple Shear tests. The resulting experimental data were used in the calibration of a number of leading constitutive models for sands during the LEAP-2020 prediction exercise. The dataset may be used in the assessment of the performance of current and future constitutive models for sands.more » « less
-
null ; null ; null (Ed.)Constitutive modeling of granular materials such as sands, non-plastic silts, and gravels has been significantly advanced in the past three decades. Several new constitutive models have been proposed and calibrated to simulate the results of various laboratory element tests. Due to this progress and owing to the surge of interest in geotechnical engineering community to use well-documented constitutive models in major geotechnical projects, a more thorough evaluation of these models is necessary. Performance of the current models should be particularly evaluated in the simulation of boundary value problems where stress/strain paths are much more complex than the element tests performed in laboratory. Such validation efforts will be an important step towards the use of these models in practice. This paper presents the results of an extensive validation study aimed at assessing the capabilities and limitations of a two-surface plasticity model for sands in two selected boundary value problems, i.e. lateral spreading of mildly sloping liquefiable grounds. The results of a large number of centrifuge tests conducted during the course of four consecutive international projects known as Liquefaction Experiments and Analysis Project (LEAP) are used in this validation study. The capabilities and limitations of the two-surface plasticity model, initially calibrated against element tests, will be carefully assessed by comparing the numerical simulations with the results of the centrifuge tests from recent LEAP projects.more » « less
-
This project documents an extensive series of laboratory tests performed at the George Washington University to characterize the basic properties and stress-strain-strength response of Ottawa F-65 sand in cyclic loading conditions. The results of these experiments as well the monotonic and cyclic triaxial tests conducted in LEAP-2015 project were provided to all the numerical simulation teams who participated in the LEAP-2017 prediction exercise. The simulation teams used these results to calibrate the constitutive models that they planned to use in numerical simulations of LEAP-2017 centrifuge tests.more » « less
-
The results of a series of nonlinear finite element simulations are presented to demonstrate the effects of base motion variability on liquefaction-induced lateral spreading of mildly sloping grounds. The analyses are part of the 2017 Liquefaction Experiments and Analysis Project (LEAP-2017). A key objective of LEAP is to generate a database of reliable centrifuge experiments to facilitate the validation of the current state-of-the-art analysis tools for the modeling of soil liquefaction. In the context of centrifuge experiments, the sources of uncertainty in the base motion are the magnitude and frequency content differences between the target and the achieved base motions. While centrifuge experiments are conducted with diligence, achieving the target base motion is restricted by the machine limitation and the presence of noise. A series of Monte Carlo (MC) simulations are performed to investigate the effects of the base motion variability. Base motion statistics are obtained as a function of frequency capturing the variations observed in the spectral accelerations of the achieved base motions. The simulations presented in this paper consider the cases of homogeneous soil as well as spatially variable soil conditions. The results of the MC simulations are used to shed light on how small deviations of the achieved base motion from the target motion might influence the response of liquefiable ground. Sensitivity of the computed soil responses to these deviations are assessed by considering the variations of excess pore pressures, lateral spreading, and ground surface settlements.more » « less