Abstract
This paper presents a coupled discrete‐finite element method for the investigation of shear strength of geogrid‐reinforced ballast by direct shear tests and pull‐out tests. The discrete element method (DEM) and finite element method (FEM) are employed to simulate ballast and geogrid, respectively. Irregularly shaped ballast particles are modeled with clumps, and the nonlinear contact force model is used to calculate contact force between particles. Continuum geogrid is modeled by a two‐node beam element with six degrees of freedom. A contact algorithm based on the static equilibrium is proposed at the geogrid‐ballast contact surface. The simulation results indicate that shear strengths increase with the installation of geogrid. Moreover, ballast particle displacements and nominal volumetric strains are analyzed to provide a microscopic view on the mechanism of the reinforcement effect of geogrid.
Highlights
In order to ensure the stability of geotechnical materials, appropriate reinforcement measures are very necessary [1]
E interaction between geogrid and ballast is an interaction of structure with granular media. e coupling of the finite element method (FEM) with the DEM is an effective approach for such problems [18,19,20]. e finite element method is used to model the continuum structure, and the discrete element method is used to model discrete particles
In the reinforced specimen, the strain distribution is mainly located above the geogrid, and an obvious shear band can be observed. e dislocation of ballast particles is not obvious during the shearing process under the unreinforced case, and the nominal volumetric strain of ballast particles on the shearing surface is not obvious. e installation of geogrid provides horizontal and lateral constraints to ballast particles along shearing surface, which results in an obvious slide of particles and shear band in the upper box. e geogrid is helpful for the stability of particles in the lower box
Summary
In order to ensure the stability of geotechnical materials, appropriate reinforcement measures are very necessary [1]. As an effective numerical approach, the discrete element method has been used to analyze the geogrid-reinforced ballast behaviors [8, 9]. E coupling of the finite element method (FEM) with the DEM is an effective approach for such problems [18,19,20]. Researchers have conducted some useful studies on the coupled discrete-finite element method. Tran et al [21] developed a coupled finite-discrete framework to investigate the behavior of a biaxial geogrid sheet embedded in granular soil and subjected to pull-out loading. E contact algorithm at the interface of structure and granular media is the key of the coupled discrete-finite method. A coupled discrete-finite element method is developed to analyze the shear strength of geogrid-reinforced ballast by direct shear tests and pull-out tests. A contact algorithm is proposed at the geogridballast contact surface. e reinforcement effect of geogrid is investigated by contrasting the results of direct shear tests and pull-out tests
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