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Introduction
Publications
Publications (47)
In this work, a fatigue crack propagation model is proposed using the two‐dimensional discrete element method (DEM). The challenge lies in describing the small progressive fatigue crack growth within a single cycle, which is typically much smaller than the size of the smallest particles, making it difficult to continuously capture the loss of conta...
A new molecular dynamics-like modelling approach aimed at simulating the mechanical behaviour of true polyhedra dense assemblies is presented. Thanks to an improved version of the Gilbert-Johnson-Keerthi contact detection algorithm called GJK − TD, this approach involves no edge or corner rounding and accounts for multipoint face − face or edge − f...
The present paper sheds new light on ongoing drawbacks of three classical algorithms dedicated to initial contact detection between overlapping convex polyhedra, (i) Cundall's common plane, (ii) Nezami's fast common plane and (iii) Gilbert-Johnson-Keerthi's algorithm (GJK). Solutions to these drawbacks are suggested and implemented into revised ver...
This work deals with the effect of the contact location distribution on the crushing of granular materials. At first, a simple drop weight experiment was designed in order to study the effect of the location of three contact edges on the fracture pattern and the strength of a model cylindrical particle. The sample was placed on two bottom contact e...
This work deals with the effect of the contact location distribution on the crushing of granular materials. At first, a simple drop weight experiment was designed in order to study the effect of the location of three contact edges on the fracture pattern and the strength of a model cylindrical particle. The sample was placed on two bottom contact e...
We study water transfer between different model fine recycled concrete aggregates and fresh filler or cement paste in which they are immersed. Our aim is to introduce a spread based experimental protocol for studying the time evolution of water content in initially dry aggregates when mixed with such pastes. The procedure developed hereby is tested...
Three-dimensional discrete numerical simulation is used to investigate the properties of close-
packed frictionless granular assemblies as a function of particle polydispersity and shape. Unlike
some experimental results, simulations show that disordered packings of pinacoids (eight-face convex
polyhedron) achieve higher solid fraction values than...
Three-dimensional discrete numerical simulation is used to investigate the properties of close-packed frictionless granular assemblies as a function of particle polydispersity and shape. Unlike some experimental results, simulations show that disordered packings of pinacoids (eight-face convex polyhedron) achieve higher solid fraction values than a...
This work deals with the effect of the contact orientation distribution on the crushing of granular materials. At first, a simple drop weight experiment was designed in order to study the effect of the location of three contact edges on the fracture pattern and the strength of a model cylindrical particle. The sample was placed on two bottom contac...
Discrete Element Methods (DEM) are a useful tool to model the fracture of cohesive granular materials. For this kind of application, simple particle shapes (discs in 2D2D, spheres in 3D3D) are usually employed. However, dealing with more general particle shapes allows to account for the natural heterogeneity of grains inside real materials. We pres...
Results of a European round-robin aiming to identify and quantify scattering sources impacting the polished stone value (PSV) of aggregates, and to assess the reference PSV of Herrnholzer granite, are presented and discussed. This reference value corrected against quartz dolerite control stone is calculated as PSVrefHE = 56.1 ± 0.5. According to va...
An experimental setup designed to capture the saturated surface dry (SSD) state of porous fine aggregates incorporating significant amounts of fines is presented. This setup is validated upon testing fine aggregate sources with different water absorption values up to 5.6%, and at least 8% of fines. Test duration is found to lie in the 120-to-240-mi...
Clay fines are known to reduce the water resistance of bitumen-aggregates binding and cause stripping in Asphalt Concrete (AC) mixtures. To address this phenomenon, a better understanding of the mineralogical composition of aggregates is needed as well as an assessment of the bitumen-clay-water interactions. This paper contributes to reach this goa...
An experimental setup designed to capture the saturated surface dry (SSD) state of porous fine aggregates incorporating significant amounts of fines is presented. This setup is validated upon testing fine aggregate sources with different water absorption values up to 5.6 %, and at least 8 % of fines. Test duration is found to lie in the 120-to-240-...
MECC2014 - 7th MID-EUROPEAN CLAY CONFERENCE, DRESDE, ALLEMAGNE, 16-/09/2014 - 19/09/2014
The present paper is a contribution to the numerical modeling of aggregate crushing that focuses on rock type aspects. Its objective is to model a unique particle as a heterogeneous assemblage of non-isotropic cohesive grains subject to uniaxial loading. A two dimensional Discrete Element Method model coupled with a Non Smooth Contact Dynamics law...
By means of numerical simulations, we study the influence of confinement on three-dimensional random close packed (RCP) granular materials subject to gravity. The effects of grain shape (spherical or polyhedral) and polydispersity on this dependence are investigated. In agreement with a simple geometrical model, the solid fraction is found to decre...
Most European countries are active in the field of recycling road materials, but knowledge and practice differ between countries. The European project DIsmantling and RECycling Techniques for road MATerials – Sharing knowledge and practices aims at sharing knowledge and practice in this field among the 15 participating countries, with the view of d...
Most European countries are active in the field of recycling road materials, but knowledge and practice differ between countries. The European project DIsmantling and RECycling Techniques for road MATerials - Sharing knowledge and practices aims at sharing knowledge and practice in this field among the 15 participating countries, with the view of d...
We study numerically the influence of confinement on the solid fraction and
on the structure of three-dimensional random close packed (RCP) granular
materials subject to gravity. The effects of grain shape (spherical or
polyhedral), material polydispersity and confining wall friction on this
dependence are investigated. In agreement with a simple g...
The influence of grain angularity on the properties of dense flows down a rough inclined plane are investigated. Three-dimensional numerical simulations using the nonsmooth contact dynamics method are carried out with both spherical (rounded) and polyhedral (angular) grain assemblies. Both sphere and polyhedra assemblies abide by the flow start and...
This paper describes the DIRECT-MAT web database which gathers European knowledge and practices about the demolition and road-recycling or safe disposal of old road materials. This database has been developed within a three-year coordination and support action under the EC 7th Framework program “Sustainable Surface Transport” for the purpose of sup...
Most European nations use washed sand to design their bituminous mixtures for wearing course, primarily to prevent excessive water sensitivity of asphalt due to the presence of clays in sand natural fines. The lack of fines is then offset by an addition of limestone filler. These practices lead to high water and energy consumption. France, Belgium...
The performance of ballasted railway tracks is largely controlled by the condition of the ballast bed. As shown on figure 1, a typical active railroad cross-section is composed of a clean ballast layer, then a transition layer of mostly clean ballast and finally a fouled ballast (or subballast) layer directly in contact with the subgrade. Subballas...
The grading curve of an aggregate is a fundamental characteristic for mix design that can easily be modified to adjust several mix properties. While sieve analysis remains the reference method to determine this curve, optical devices are developing, allowing easier and faster assessment of aggregate grading. Unfortunately, optical grading results s...
Les priorités exprimées par le Grenelle de l'environnement ont naturellement conduit le LCPC à renforcer cet engagement dans le nouveau contrat quadriennal qu'il doit prochainement passer avec l'État, en mettant l'accent sur la thématique scientifique prioritaire "Économiser l'énergie et les ressources naturelles". L'un des volets de cette thématiq...
DIRECT-MAT est l'acronyme d'un projet européen de trois ans, piloté par le LCPC, visant à faciliter le partage à l'échelon européen des expériences nationales de déconstruction et de recyclage dans la route ou de mise en décharge sécurisée des matériaux routiers au sens large. Il a été initié, dans le cadre du FEHRL, lors du premier appel à projets...
DIRECT-MAT is a three-year European project aiming to facilitate the sharing of national experiences on dismantling and recycling or safe disposal of road and road related materials at the European level. It was initiated within the EC 7th Framework Programme Transport first call and is comprised of partners from fifteen participating countries for...
Aggregate shape is a key parameter that influences mixtures properties. This paper accounts for a closely controlled experimental program aimed at clarifying the variation of aggregate shape with two parameters, gyratory crusher setting and feed grading. The results show that crusher setting has a significant influence on the flakiness index of pro...
The angularity of coarse aggregates, as a parameter exerting a well-established influence on the behavior of asphalt pavement layers, can be determined by means of the European flow test using the angulometer. Yet, the relationship between flow coefficient and the set of geometric and petrographic properties of aggregates remains uncertain, which h...
This paper first describes an efficient image processing based subroutine aimed at assessing railroad ballast wear stage through particle angularity characterization. Three main conclusions were drawn from subsequent experimentations: first, ANG criterion can detect a light wear stage; second, the criterion is very discriminatory; third, ANG values...
Recent research achieved on recycled railway ballasts issued that they were not properly assessed using European standard test methods. Indeed, other characteristics such as wear stage of particles have to be checked to assess their resistance to tracks vertical deformations. This paper introduces a new image processing based method and angularity...
A new image processing based test method has been developed, in order to assess the percentage of crushed and broken surfaces in alluvial coarse aggregate. This test method has been implemented into the VDG40 videograder and an effective test procedure has been set. Indeed, the analysis of a 1 kg 6/10-mm sample only requires less than three minutes...
Aggregate shape is considered to be a key parameter for concrete and bituminous mixtures design. Generally, this parameter
is determined by calculating a ratio between the different dimensions of the particles and by comparing this ratio to a flatness
or elongation limit. The standardized methods used for this purpose vary among countries, but all...
This study's objective is twofold: to gain an understanding of the causes of poor reliability in the sand flow test with a 0.08/2-mm particle size fraction, as set forth in French standards NF P 18-564 and European standards NF EN 933-6 ; and to propose an economical and efficient solution for improving this reliability. The study indicates that 90...
An experimental study of the mechanisms that govern the hydraulic fracturing of Vire granite samples is presented. Four blocks were subjected to controlled injection of water in a grooved borehole. The pressure and volume of the injected water and the length and width of the fractures were monitored. When the depth of the grooving was one third of...
In France, different aggregate fractions are required for public construction, depending on the type of structure to be built. The size control performed on all aggregate brands traditionally consists in grading tests, using ISO fraction sieves. This kind of control is rather expensive, time-consuming, and, sometimes too slow in regard to the build...