Abstract
A numerical model based on the finite element framework was developed to predict the seismic response of saturated sand under free-field conditions. The finite element framework used a non-linear coupled hypoplastic model based on the u-p formulation to simulate the behaviour of the saturated sand. The u-p coupled constitutive model was implemented as a user-defined routine in commercial ABAQUS explicit 6.14. Results of centrifuge experiments simulating seismic site response of a layered saturated sand system were used to validate the numerical results. The centrifuge test consisted of a three-layered saturated sand system subjected to one-dimensional seismic shaking at the base. The test set-up was equipped with accelerometers, pore pressure transducers, and LVDTs at various levels. Most of the constitutive models used to date for predicting the seismic response of saturated sands have underestimated volumetric strains even after choosing material parameters subjected to rigorous calibration measures. The hypoplastic model with intergranular strains calibrated against monotonic triaxial test results was able to effectively capture the volumetric strains, reasons for which are discussed in this paper. The comparison of the numerical results to centrifuge test data illustrates the capabilities of the developed u-p hypoplastic formulation to perform pore fluid analysis of saturated sand in ABAQUS explicit, which inherently lacks this feature.
Highlights
Soil liquefaction caused by earthquake loading is a major threat to infrastructure
Bulk modulus of the solid grains (Ks) is the bulk modulus of the solid grains, Bulk modulus of water (Kw) is the bulk modulus of water, vs is the current velocity of the solid phase, k is the permeability of the solid skeleton, μw is the viscosity of fluid, Bulk modulus of the solid skeleton (KT) is the bulk modulus of the solid skeleton, E is the Young’s modulus of the solid skeleton and ν is the Poisson’s ratio of the solid skeleton
A u-p based formulation coupled with hypoplastic constitutive model was developed as a single VUMAT to be used with commercial ABAQUS Explicit software, which does not possess in-built capability to model pore fluid pressures
Summary
Soil liquefaction caused by earthquake loading is a major threat to infrastructure. Loose saturated sands when subjected to seismic loading develop high excess pore water pressures that may lead to soil liquefaction. The liquefaction prediction capability of these constitutive models has been evaluated by comparing the simulation results to element level tests or centrifuge experimental results for single saturated soils [6,7,8]. Tasiopoulou et al [10] used the framework developed by Jeremic et al [9] to capture the behaviour of saturated sands under seismic loading and compared the results to centrifuge test results. In this work, a coupled u-p formulation based on the hypoplastic model with intergranular strains was used in ABAQUS 6.14 explicit to predict soil response of layered saturated sand under seismic excitation.
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