Showing papers by "Fang-Le Peng published in 2010"

FEM simulation of viscous properties for granular materials considering the loading rate effect

Abstract: The deformation and strength characteristics of sandy soils as a kind of granular materials are very complex. The experimental results show that when the strain rate suddenly changes in monotonic loading (ML) case, the stress–strain curve of sandy soils changes sharply and then gradually converges into the original inferred one that would be obtained by continuous ML at constant strain rate after having exhibited clear yielding. Similar behaviors are also observed when ML is restarted at a constant strain rate following a creep loading or stress relaxation stage. An elasto-viscoplastic constitutive model for granular materials is developed, which consists of three components. One of the most important features of the model is that it can take into account the effects of loading rate due to viscous properties on the stress–strain behavior. The stress ratio-axial strain–time relations from four drained plain strain compression (PSC) tests on the saturated Toyoura sand are successfully simulated by the finite element method (FEM) code incorporating the proposed constitutive model. It is shown that the FEM code can simulate the viscous behaviors of sand accurately under arbitrary loading history.

Effects of loading rate on viscoplastic properties of polymer geosynthetics and its constitutive modeling

Abstract: On the basis of the special tensile test results under various loading histories, the rate-dependent behaviors of three polymer geosynthetics due to their viscous properties have been investigated. All the investigated polymer geosynthetics show significant loading rate effects, creep deformation, and stress relaxation. Except for the polyester geogrid showing the combined viscosity, all the investigated polymer geosynthetics exhibit the isotach viscosity. An elasto-viscoplastic constitutive model described in a nonlinear three-component model framework is developed to simulate the rate-dependent behaviors of polymer geosynthetics. The developed constitutive model is verified by comparing its simulated results with the experimental data of polymer geosynthetics presented in this study and those available from the literature. The comparison indicates that the developed model can reasonably interpret the rate-dependent behaviors of polymer geosynthetics under arbitrary loading histories, including the step-changed strain rate loading, creep, and stress relaxation applied during otherwise monotonic loading (ML). POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

Semiempirical Approach for Estimation of DDC-Induced Deflections of Sheet Pile Walls in Peat

Abstract: With an inclinometer casing mounted on a sheet pile wall in peat bogs, sheet pile wall deflections were measured during a trial deep dynamic compaction (DDC) test. Analyses of the trial testing data indicated that sheet pie wall deflections were significantly affected by the tamping distance, X , (horizontal distance between tamping points and sheet pile walls). The DDC-induced wall deflections can be simulated by an exponential relationship related to X . The trial testing results were verified by the finite-element (FE) simulation. The FE analyses indicated that sheet pile wall deflections were linearly proportional to the impact energy per blow, Ei . The analyses of surveyed data showed that sheet pile wall deflections due to DDC were also related to the ratio of the wall penetration depth in the underlying sands, dS , to the wall height, L . Based on these findings, a semiempirical approach, incorporating the key factors that govern the sheet pile wall deflections during DDC, was developed. The estima...

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.