Modelling of rutting of two flexible pavements with the shakedown theory and the finite element method

This paper presents a finite element program, for the modelling of rutting of flexible pavements. In its present version, the program incorporates a permanent deformation model for unbound granular materials based on the concept of the shakedown theory developed by Zarka for metallic structures under cyclic loadings and has been used to estimate the permanent deformations of unbound granular materials (UGM) subjected to traffic loading. The calculation is performed in two steps: the first step consists in modelling the resilient behaviour of the pavement in 3D, using non-linear elastic models, to determine the stress field in the pavement. Then stress paths are derived and used to calculate the permanent deformations and the displacements, using a Drucker–Prager yield surface. An application to the prediction of the permanent deformations of experimental pavements with an unbound granular base, tested on the LCPC pavement testing facility is presented.     

A two‐mechanism elastoplastic model for shakedown of unbound granular materials and DEM simulations

An elastoplastic model has been developed for the finite elements modelling of repeated load triaxial tests. This model is based on the shakedown theory established by Zarka for metallic structures. To the previous works, which were based on the Drucker–Prager yield surface and the plastic potential of Von Mises, a compression cap has been added to each one. The model straightforwardly determines the purely elastic state or the elastic shakedown state or the plastic shakedown state and calculates the deviatoric and the volumetric plastic strains. The calibration of the elastoplastic model has been carried out with DEM simulations and an unbound granular material for roads under repeated load triaxial tests using finite element method. The calculations underline the capabilities of the model to take into account, with a unique formalism, the accumulation of the deviatoric and volumetric plastic strains along the loading cycles. Copyright © 2011 John Wiley & Sons, Ltd.     

Non‐coaxial elasto‐plasticity model and bifurcation prediction of shear banding in sands

Numerous constitutive models built on coaxial theory and validated under axi‐symmetric condition often describe the stress–stain relationships and predict the inceptions of shear banding in sands inaccurately under true triaxial condition. By adopting an elaborated Mohr–Coulomb yield function and using non‐coaxial non‐associated flow rule, a 3D non‐coaxial elasto‐plasticity model is proposed and validated by a series of true triaxial tests on loose sands. The bifurcation analysis of true triaxial tests on dense sands predicts the influence of the intermediate principal stress ratio on the onset of shear band accurately. The failure of soils is shown to be related to the formation of shear band under most intermediate principal stress ratio conditions except for those which are close to the axi‐symmetric compression condition. Copyright © 2009 John Wiley & Sons, Ltd.     

Elasto‐plastic modelling of stress‐path‐dependent behaviour of interfaces

A single‐surface elasto‐plastic model developed by Desai and his coworkers is used to predict the behaviour of an interface between sand and a steel plate. The loading in the experiments and in their predictions followed various stress and displacement paths. The results of predictions of the two‐ and three‐dimensional behaviour of the interface under both constant normal stress and constant normal stiffness conditions are presented. The predictions are compared with their corresponding experimental results. The model parameters were determined on the basis of 2‐D conventional experiments under the condition of constant normal stress and they were used in the prediction of the interface behaviour in various stress paths. There is, in general, a good agreement between the predicted and experimental results. Copyright © 2000 John Wiley & Sons, Ltd.     

Three dimensional elasto‐plastic interface for embedded beam elements with interaction surface for the analysis of lateral loading of piles

This paper presents a numerical formulation for a three dimensional elasto‐plastic interface, which can be coupled with an embedded beam element in order to model its non‐linear interaction with the surrounding solid medium. The formulation is herein implemented for lateral loading of piles but is able to represent soil‐pile interaction phenomena in a general manner for different types of loading conditions or ground movements. The interface is formulated in order to capture localized material plasticity in the soil surrounding the pile within the range of small to moderate lateral displacements. The interface is formulated following two different approaches: (i) in terms of beam degrees of freedoms; and (ii) considering the displacement field of the solid domain. Each of these alternatives has its own advantages and shortcomings, which are discussed in this paper. The paper presents a comparison of the results obtained by means of the present formulation and by other well‐established analysis methods and test results published in the literature. Copyright © 2016 John Wiley & Sons, Ltd.     

Application of numerical modelling in the design of a full‐scale heated Tunnel Sealing Experiment

The Tunnel Sealing Experiment (TSX) was a full‐scale in situ demonstration of technology for constructing nearly water tight‐seals in excavations through crystalline rock deep below the surface of the earth. The experiment has been carried out at Atomic Energy of Canada Limited's (AECL's) Underground Research Laboratory near Lac du Bonnet, Canada, in support of international programs for geologic disposal of radioactive waste. The TSX, with partners from Canada, Japan, France and the United States, was carried under conditions of high pressure (up to 4 MPa) and elevated temperature (up to 85°C). Comparing numerical model predictions with eight years of data collected from approximately 900 sensors was an important component of this experiment. Model of Transport In Fractured/porous Media (MOTIF), a finite element computer program developed by AECL for simulating fully coupled or uncoupled fluid flow, solute transport and heat transport, was used to model both the ambient temperature and heated phases of the TSX. The plan to heat the water in the TSX to 85°C was developed using model predictions and a comparison of simulated results with measurements during heating of the water in the TSX to about 50°C. The three‐dimensional MOTIF simulations were conducted in parallel with axisymmetric modelling using Fast Lagrangian Analysis of Continua (FLAC), which computed the heat loss from pipes that carried the heated water through the rock to and from the experiment. The numerical model was initially used to develop a plan for operation of the experiment heaters, and then subsequently used to predict temperatures and hydraulic heads in the TSX bulkhead seals and surrounding rock. Copyright © 2005 John Wiley & Sons, Ltd.