The choice of structure element to simulate soil reinforcement and soil–structure interaction details for numerical modelling of mechanically stabilized earth (MSE) walls can have a significant influence on numerical outcomes. Program FLAC (finite difference method) offers three different options (beam, cable and strip element) to model the reinforcement and program PLAXIS (finite element method) has two (beam and geogrid element). Both programs use different models and properties to simulate the mechanical behaviour of the interface between dissimilar materials. The paper describes the details of the linear elastic Mohr–Coulomb interface model available in the two software packages to model material interaction and how to select model parameters to give the same numerical outcomes. The numerical results quantitatively demonstrate the conditions that give good agreement between the two programs for the same steel strip reinforced soil–structure problem and the situations where they do not. For example, the paper demonstrates that results can be very different depending on the type of structure element used to model horizontal reinforcement layers that are discontinuous in the plane-strain direction.
Damians, I.P.; Bathurst, R.J.; Josa, A.; Lloret, A. International journal of geomechanics Vol. 15, num. 1, p. 04014037-1-04014037-15 DOI: 10.1061/(ASCE)GM.1943-5622.0000394 Date of publication: 2015-02-01 Journal article
The paper describes the results and lessons learned using aFEMmodel to simulate quantitative performance features of the Minnow Creek steel- strip reinforced soil wall structure located in the United States. The Minnow Creek Wall structure was constructed and instrumented in 1999. It is a unique case study because of the comprehensive measurements that were taken to record a wide range of wall performance features. Two different constitutive models for the soil were used (a linear- elastic Mohr- Coulomb model and hardening soil model with a Mohr- Coulomb failure criterion), and numerical outcomes were compared with physical measurements. The numerical results were shown to be sensitive to boundary conditions assumed at the toe of the wall. The generally encouraging agreement between physical and numerically predicted results gives confidence that commercial FEMsoftware packages can be useful for the analysis and design of these types of structures, provided that care is taken in the selection of input parameters. (C) 2014 American Society of Civil Engineers.
The choice of structure element to simulate soil reinforcement and soil-structure interaction details for numerical modelling of mechanically stabilized earth (MSE) walls can have a significant influence on numerical outcomes. Program FLAC (finite difference method) offers three different options (beam, cable and strip) to model the reinforcement and program PLAXIS (finite element method) has only one (“geogrid” element). Both programs use different models and properties to simulate the mechanical behavior of the interface between dissimilar materials. The paper describes the details of the Mohr-Coulomb interface model available in the two software packages to model material interaction and how to select model parameters to give the same numerical outcomes. The numerical results quantitatively demonstrate the conditions that give good agreement between the two programs for the same reinforced soil-structure problem and the situations where they do not. For example, the paper demonstrates that results can be very different depending on the type of structure element used to model horizontal reinforcement layers that are discontinuous in the plane-strain direction. // Le choix des éléments structuraux pour simuler les détails des renforcements de sol et l’interaction s
ol-structure pour la modélisation numérique des murs en sol renforcé, peut avoir une influence significative sur les résultats numériques. Le programme FLAC (méthode des différences finis) offre trois différentes options (poutre, câble et languette) pour modéliser le renforcement et le programme PLAXIS (méthode des éléments finis) n’en n’a qu’un seul (l’élément « géogrille »). Les deux programmes utilisent différents modèles et propriétés pour simuler le comportement mécanique de l’interface entre des matériaux dissimilaires. L’article décrit les détails du modèle d’interface de Mohr-Coulomb disponible dans les deux logiciels pour modéliser l’interaction entre les matériaux et décrit comment choisir les
paramètres du modèle pour obtenir les mêmes résultats numériques. Les résultats numériques démontrent quantitativement les conditions qui mènent à un bon accord entre les deux programmes, pour le même problème d’interaction sol renforcé–structure, et les situations où il n’y a pas accord. Par exemple, l’article démontre que les résultats peuvent être très différents dépendant du type d’élément structural utilisé pour modéliser des couches derenforcement horizontales qui sont discontinues dans la direction des déformations plane
Damians, I.P.; Bathurst, R.J.; Josa, A.; Lloret, A. International journal of geotechnical engineering Vol. 8, num. 3, p. 247-259 DOI: 10.1179/1939787913Y.0000000039 Date of publication: 2014-07-01 Journal article
Most geosynthetic and metallic reinforced soil walls are designed assuming that the wall foundation is rigid and/or does not influence the magnitude and distribution of reinforcement loads under operational conditions. This assumption may not apply to walls constructed over compliant (compressible) foundations. This paper describes the results of a series of numerical simulations that were carried out on idealized 3·6, 6, and 9 m-high modular block walls seated on foundations having four different compressibility values. The walls were constructed with two reinforcement materials having very different stiffness values but the same tensile strength. The results of simulations show that as foundation stiffness decreases, reinforcement loads increase. However, for the two reinforcement materials in this study, the influence of axial stiffness of the reinforcement had a greater effect on wall performance than the foundation stiffness for walls subjected to operational (working stress) conditions at end of construction.
Damians, I.P.; Bathurst, R.J.; Josa, A.; Lloret, A. International Conference on Soil Mechanics and Geotechnical Engineering p. 1959-1962 Presentation's date: 2013-09-02 Presentation of work at congresses
Current design practices for reinforced soil walls typically ignore the influence of facing type and foundation compressibility on the magnitude and distribution of reinforcement loads in steel reinforced soil walls under operational conditions. In
this paper, the effect of the facing vertical stiffness (due to elastomeric bearing pads placed in the horizontal joints between panels) on load capacity of steel reinforced soil walls is examined in a systematic manner using a numerical modelling approach. Numerical modelling was carried out using the commercial finite element program PLAXIS. The numerical model was verified against
measurements recorded for an instrumented 6 m-high wall reinforced with steel strips. The influence of the facing stiffness and backfill-foundation stiffness combinations on the vertical load through the facing and on the magnitude and distribution of the reinforcement loads was examined. For walls subjected to operational (working stress) conditions at end of construction, the numerical results confirm that the vertical stiffness of the facing and soil-stiffness combinations can have a great effect on the vertical facing loads and on the magnitude and distribution of the load mobilized in the soil reinforcement layers.
The paper investigates the influence of backfill soil, foundation soil, and horizontal joint vertical compressibility on the magnitude of vertical loads developed in steel-reinforced soil concrete panel retaining walls at the end of construction. Measurements of toe loads recorded from instrumented field walls are reviewed and demonstrate that vertical toe loads can be much larger than the self-weight of the facing. In extreme cases, these loads can result in panel-to-panel contact leading to concrete spalling at the front of the wall. Vertical loads in excess of panel self-weight have been ascribed to relative movement between the backfill soil and the panels that can develop panel-soil interface shear and downdrag loads at the connections between the panels and the steel-reinforcement elements. A two-dimensional finite-element model is developed to systematically investigate the influence of backfill soil, foundation soil, bearing pad stiffness, and panel-soil interaction on vertical loads in the panel facing. The results show that an appropriately selected number and type of compressible bearing pads can be effective in reducing vertical compression loads in these structures and at the same time ensure an acceptable vertical gap between concrete panels. The parametric analyses have been restricted to a single wall height (16.7 m) and embedment depth of 1.5 m, matching a well-documented field case. However, the observations reported in the paper are applicable to other similar structures. The general numerical approach can be used by engineers to optimize the design of the bearing pads for similar steel-reinforced soil wall structures using available commercial finite-element model packages together with simple constitutive models.
This document presents preliminary results of FEM-numerical analysis of soilreinforcement pullout tests. The numerical model has been developed with CODE_BRIGHT and assuming the interfaces as continuum materials. The results of the preliminary parametric analyses described herein provide useful information on the shear behavior modeling of soil-reinforcement strip interfaces under working stress conditions
Damians, I.P.; Josa, A.; Albuquerque, P.J.R.; Lloret, A.; Ledesma, A.; de Santos, C. Pan-Am CGS Geotechnical Conference. Pan-American Conference on Soil Mechanics and Geotechnical Engineering. Canadian Geotechnical Conference. Pan-American Conference on Teaching and Learning of Geotechnical Engineering p. 1-9 Presentation's date: 2011-10-03 Presentation of work at congresses