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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.
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Effects of Small Variability of Soil Density on the Consequences of Liquefaction
The effects of small inherent variability of soil density on the consequences of liquefaction such as lateral spreading and excessive settlements may have significant practical implications. Here, the effect of variability on soil density is evaluated for mildly sloping soil specimens that are tested in a series of centrifuge tests at different facilities. While every effort was made to prepare the specimens with uniform densities, the achieved densities at different facilities showed a small variation relative to the target density. This paper presents an attempt to investigate the impact of such variability on the expected response of the soil, particularly when it reaches a liquefaction state. A Monte Carlo simulation was conducted using a non-linear effective stress analysis and an elastoplastic constitutive model for sand. The simulation results show that the small variation of density in the soil specimen leads to a relatively small range of variation for lateral displacements, acceleration, and excess pore pressure ratios. However the range of settlements calculated on the ground surface was rather large, with the coefficient of variation ranging from 8% to 30% depending on the type of variability considered. Potential reasons for such drastic differences among various components of the soil response are discussed.
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- Award ID(s):
- 1635524
- PAR ID:
- 10036284
- Date Published:
- Journal Name:
- Geo-Risk 2017
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/http://ascelibrary.org/doi/abs/10.1061/9780784480700.002
