Effect of flexible membrane in large-scale triaxial test DEM simulations

• Published in: Construction & building materials 2023-03, Vol.370, p.130608, Article 130608
• Main Authors: Huang, Shihao, Qian, Yu, Shan, Yao
• Format: Article
• Language: English
• Subjects: Discrete element method; Extra confinement; Flexible membrane; Membrane stiffness; Railway ballast; Triaxial test
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2023.130608

•Potential redundant restrain to the specimen from membrane contact stiffness parameters in DEM simulations are investigated.•The correlation between the membrane element contacts stiffness and size, and the imposed redundant confinement is quantified.•Explains the discrepancy between the DEM simulations and laboratory triaxial experiments with railroad ballast aggregates.•A correction function is proposed. The use of flexible membrane boundaries in simulations of ballast triaxial tests with the discrete element method (DEM) has become increasingly popular, due to the benefits of more uniform confining pressure and realistic specimen deformation. However, it is not well understood whether the simulated flexible membranes may lead to overstated results due to extra confinement of the specimen. To investigate this, a series of three-dimensional (3D) discrete element simulations were performed using different flexible membrane configurations and parameters. The results showed that the flexible membrane has an effect on the stress-strain response of the specimen once axial strain exceeds 1%, and that a higher stiffness and larger element size of the membrane leads to greater extra confinement during shearing. A correlation model was developed to predict the extra confinement of the flexible membrane, which was validated to reasonably predict the restriction on triaxial test simulations.