Yong Tan

FEM simulation of deformation and strength characteristics in geogrid- reinforced sand retaining wall under the change of loading rate

It is often important in geotechnical engineering practice and research to evaluate accurately the time effect on the deformation and strength characteristics of geogrid-reinforced sand retaining wall. Loading rate effect is one of the most important time-dependent behaviors of material, which is an inherent response of the viscous property of material. Based on the Dynamic Relaxation method, the nonlinear finite element method (FEM) analysis technique was developed. In the numerical analysis, both the viscous properties of the backfill (sand) and the reinforcement (geogrid) were taken into account through the unified non-linear three-component elastic-viscoplastic model. The presented FEM is validated by simulating a physical model test on geogrid-reinforced sand retaining wall. It is shown that the aforementioned FEM can well simulate the deformation and strength behaviors of geogrid-reinforced sand retaining wall under the change of loading rate, such as the overall footing pressure - settlement relationship and the earth pressure.

FEM analyses on creep characteristics and strain fields of geogrid-reinforced sand

ABSTRACT Both sand and polymer geogrid reinforcement are known to exhibit more-or-less complicated stress-strain-time or load-strain-time behavior including instantaneous non-linearity and viscous effects. Creep is one of the most important time-dependent behaviors of material, which is an inherent response of the viscous property of material. Due to interactions between the viscous sand and reinforcement, the creep characteristics of geogrid-reinforced sand could be very complicated. A nonlinear finite element method (FEM) analysis technique incorporating the unified three-component elasto-viscoplastic constitutive model for both sand and geogrid was developed. The FEM can simulate the whole process including the constant strain rate loadings and the creep loading stages. In addition, the development of strain fields during the creep loading can also be reproduced by the FEM simulation. By comparing the simulated results with the experimental results, it was shown that the proposed elasto-viscoplastic FEM could well simulate the creep characteristics of geogrid-reinforced sand, especially for the high stiffness following a creep loading stage.

Simulating Rate-Dependent Behavior of Geogrid-Reinforced Sands by FEM

ABSTRACT A nonlinear finite element method (FEM) analysis technique incorporating the non-linear three-component elasto-viscoplastic constitutive models for both sands and polymer geogrids is developed. The model can describe the viscous effects on the stress-strain or tensile load-strain behavior observed in a series of comprehensive laboratory tests on clean sands or geogrids. The dynamic relaxation technique combined with the return mapping algorithm is applied to the inte gration algorithms of viscoplastic constitutive relations, including the effects of loading rate, stress path and shear band. A series of plane strain compression (PSC) tests performed on geogrid-reinforced sands were simulated by the FEM. The simulated average stress ratio and vertical strain relations of geogrid-reinforced sands were compared with the measurements. It is shown that the developed FEM analysis method can simulate the test results very well, especially for loading rate effects, creep and stress relaxation.