Comparison of finite element and finite difference modelling results with measured performance of a reinforced soil wall (original) (raw)
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Numerical Model for Reinforced Soil Segmental Walls under Surcharge Loading
Journal of Geotechnical and Geoenvironmental Engineering, 2006
The construction and surcharge loading response of four full-scale reinforced-soil segmental retaining walls is simulated using the program FLAC. The numerical model implementation is described and constitutive models for the component materials ͑i.e., modular block facing units, backfill, and four different reinforcement materials͒ are presented. The influence of backfill compaction and reinforcement type on end-of-construction and surcharge loading response is investigated. Predicted response features of each test wall are compared against measured boundary loads, wall displacements, and reinforcement strain values. Physical test measurements are unique in the literature because they include a careful estimate of the reliability of measured data. Predictions capture important qualitative features of each of the four walls and in many instances the quantitative predictions are within measurement accuracy. Where predictions are poor, explanations are provided. The comprehensive and high quality physical data reported in this paper and the lessons learned by the writers are of value to researchers engaged in the development of numerical models to extend the limited available database of physical data for reinforced soil wall response.
Influence of toe restraint on reinforced soil segmental walls
Canadian Geotechnical Journal, 2010
A verified fast Lagrangian analysis of continua (FLAC) numerical model is used to investigate the influence of horizontal toe stiffness on the performance of reinforced soil segmental retaining walls under working stress (operational) conditions. Results of full-scale shear testing of the interface between the bottom of a typical modular block and concrete or crushed stone levelling pads are used to back-calculate toe stiffness values. The results of numerical simulations demonstrate that toe resistance at the base of a reinforced soil segmental retaining wall can generate a significant portion of the resistance to horizontal earth loads in these systems. This partially explains why reinforcement loads under working stress conditions are typically overestimated using current limit equilibrium-based design methods. Other parameters investigated are wall height, interface shear stiffness between blocks, wall facing batter, reinforcement stiffness, and reinforcement spacing. Computed reinforcement loads are compared with predicted loads using the empirical-based K-stiffness method. The K-stiffness method predictions are shown to better capture the qualitative trends in numerical results and be quantitatively more accurate compared with the AASHTO simplified method.
NUMERICAL MODELING OF REINFORCED SOIL SEGMENTAL WALL UNDER SURCHARGE LOADING
iaeme
This paper outlines the finite element procedure for simulating the performance of a reinforced soil segmental (modular blocks) wall. Analyses were performed using a software code which is developed in FORTRAN and validated for reported case histories in the literature. The material properties of the wall like backfill, foundation, modular concrete fascia blocks and reinforcement were expressed using linear elastic models. A series of parametric studies was conducted to identify effects of reinforcement, stiffness and Poison’s ratio of backfill and foundation strata on the performance of the wall. Increased stiffness of backfill and foundation improves the performance of the wall by restraining the front face deformation. The design charts for deflections at top and bottom and also, height of rotation are developed in the current work by varying the stiffness of backfill and foundation. These charts are useful to the designer to choose appropriate backfill and also, to ascertain the suitability of available foundation for the construction of wall, considering codal provisions regarding deformation limits at the front face of the wall.
Canadian geotechnical journal, 2005
The paper describes a numerical model that was developed to simulate the response of three instrumented, full-scale, geosynthetic-reinforced soil walls under working stress conditions. The walls were constructed with a fascia column of solid modular concrete units and clean, uniform sand backfill on a rigid foundation. The soil reinforcement comprised different arrangements of a weak biaxial polypropylene geogrid reinforcement material. The properties of backfill material, the method of construction, the wall geometry, and the boundary conditions were otherwise nominally the same for each structure. The performance of the test walls up to the end of construction was simulated with the finite-difference-based Fast Lagrangian Analysis of Continua (FLAC) program. The paper describes FLAC program implementation, material properties, constitutive models for component materials, and predicted results for the model walls. The results predicted with the use of nonlinear elastic-plastic models for the backfill soil and reinforcement layers are shown to be in good agreement with measured toe boundary forces, vertical foundation pressures, facing displacements, connection loads, and reinforcement strains. Numerical results using a linear elastic-plastic model for the soil also gave good agreement with measured wall displacements and boundary toe forces but gave a poorer prediction of the distribution of strain in the reinforcement layers.
Reinforced Soil Retaining Wall Testing, Modeling and Design
2007
This paper presents an overview of a program of physical and numerical modeling of reinforced soil walls conducted by the writer and co-workers, and the development of a new design approach for these systems. The physical testing described in the paper was carried out in a full-scale test facility at RMC and involved a series of wall models designed to isolate the contribution of facing type, reinforcement type and reinforcement arrangement on wall behaviour under serviceability conditions and surcharge loading approaching wall collapse. The numerical modeling was carried out using the program FLAC and the results verified against selected physical tests carried out at RMC. The results of physical tests carried out at RMC and data collected from instrumented structures reported in the literature has led to the development of an empirical-based design methodology (K-stiffness Method). This new approach to reinforced soil wall design has been quantitatively and qualitatively demonstrated to be much more accurate than the current limit equilibrium-based tie-back wedge design method currently used in North America.
Advances and uncertainties in the design of anchored retaining walls using numerical modelling
Acta Geotechnica Slovenica, 2008
The paper describes a research on the prediction of horizontal displacements and internal forces in an anchored wall for the protection of an excavation, by the use of standard field and laboratory tests and a finite element programme with such a soil model which can simulate the essential aspects of soil behaviour at the construction site. It is important to be acquainted with the constitutive model incorporated in the programme, and the selection of appropriate soil parameters for the numerical analysis is the crucial part of modelling. It is, thus, useful to carry out numerical simulations of standard laboratory tests with the well-known soil behaviour in order to select relevant parameters for the simulation of the actual construction process. It is shown in the paper that the measurements of shear wave velocities, which can provide the soil stiffness at very small strains, can be useful also for the determination of the static stiffness at the magnitude of strains relevant for ...
Advances and Uncertainties in Design of Anchored Retaining Walls by Numerical Modelling
2010
The paper describes a research on the prediction of horizontal displacements and internal forces in an anchored wall for the protection of an excavation, by the use of standard field and laboratory tests and a finite element programme with such a soil model which can simulate the essential aspects of soil behaviour at the construction site. It is important to be acquainted with the constitutive model incorporated in the programme, and the selection of appropriate soil parameters for the numerical analysis is the crucial part of modelling. It is, thus, useful to carry out numerical simulations of standard laboratory tests with the well-known soil behaviour in order to select relevant parameters for the simulation of the actual construction process. It is shown in the paper that the measurements of shear wave velocities, which can provide the soil stiffness at very small strains, can be useful also for the determination of the static stiffness at the magnitude of strains relevant for ...
Mathematical Problems in Engineering, 2022
Three-dimensional finite element analysis has been carried out in order to study the response of retaining walls subjected to lateral earth pressure using ABAQUS/CAE. This study consists of analysis and design of cantilever, gravity type, and precast concrete retaining wall. It also shows comparative study such as distribution of stresses along with the deflection throughout the height of the retaining walls. The mathematical analysis procedure is adopted that entails selecting dimensions to meet the requirements of several codes and then evaluating the stability of the entire whenever the backfill load works on the wall. The stability of retaining walls in terms of sliding and overturning is evaluated. The three specified walls are then investigated using the ABAQUS software, and their behaviour is studied. In this analysis process, two components of the formed concrete wall; one is a base plate and another component is a cantilever sandwich panel, were projected. A headed anchor j...
Numerical Study of Reinforced Soil Segmental Walls Using Three Different Constitutive Soil Models
Journal of Geotechnical and Geoenvironmental Engineering, 2009
A numerical finite-difference method ͑FLAC͒ model was used to investigate the influence of constitutive soil model on predicted response of two full-scale reinforced soil walls during construction and surcharge loading. One wall was reinforced with a relatively extensible polymeric geogrid and the other with a relatively stiff welded wire mesh. The backfill sand was modeled using three different constitutive soil models varying as follows with respect to increasing complexity: linear elastic-plastic Mohr-Coulomb, modified Duncan-Chang hyperbolic model, and Lade's single hardening model. Calculated results were compared against toe footing loads, foundation pressures, facing displacements, connection loads, and reinforcement strains. In general, predictions were within measurement accuracy for the end-of-construction and surcharge load levels corresponding to working stress conditions. However, the modified Duncan-Chang model which explicitly considers plane strain boundary conditions is a good compromise between prediction accuracy and availability of parameters from conventional triaxial compression testing. The results of this investigation give confidence that numerical FLAC models using this simple soil constitutive model are adequate to predict the performance of reinforced soil walls under typical operational conditions provided that the soil reinforcement, interfaces, boundaries, construction sequence, and soil compaction are modeled correctly. Further improvement of predictions using more sophisticated soil models is not guaranteed.
This paper presents a 3D finite element study on a model to simulate an horizontal load test on a retaining pile wall. The piles wall was constructed at the site of Port Ghalib marina on the Red-Sea coast of Egypt which is considered as an active seismic area. The subsoil layers consist of 2 m to 3 m gravelly sand followed by a deep clayey silt layer. The ground water was observed at a depth of about 1.10 m below ground surface. The purpose of the test is to evaluate the pile displacement characteristics under exposed loads. Numerically a 10 m – length pile was modelled to simulate the actual case. Effect of surcharge, earth pressure and earthquake loads were taken into consideration. The numerical analysis was performed and the results have been found to be in good agreement with the measured field test results. In addition the finite element method make an ability to predict the deflection along the pile length. RÉSUMÉ : Cet article présente un modèle 3D éléments de dimension par élément finie pour' simuler un chargement horizontal d'un mur de quai du port de plaisance de Port Ghalib sur les côtes égyptienne de la mer Rouge qui est une zone sismique. La stratigraphie est constitué d'une couche de 2 à 3 m de sable graveleux, en surface, suivie d'une couche de limon argileux, en profondeur. La nappe phréatique est située à 1,1 m de la surface. L'objectif de l'analyse est de caractériser le déplacement latéral du mur en fonction du chargement. Le modèle numérique a été construit pour simuler le cas réel. Les effets de la surcharge, pression des terres et effets des seismes, ont été pris en compte dans le modèle. L'analyse numérique et les résultats sont en accord avec les résultats des expérimentaux de terrain. En outre, la méthode des éléments finis donne une prédiction de la déviation le long du mur.