This study aims to examine the deformation behavior and internal mechanism of coarse-grained soil as an embankment filler under cyclic loading. Numerical dynamic triaxial tests were performed on coarse-grained soil using the discrete element software PFC3D. The numerical model was verified by comparing the numerical results with the experimental data. Afterward, the changes in the porosity, force chain, and particle movement of coarse-grained soil samples were analyzed, and the mesoscopic deformation behavior of coarse-grained soil under cyclic loading was investigated. The research results show that with the increase of the deviatoric stress amplitude, moisture content, and loading frequency, the deformation of the soil increases and the ability to resist deformation decreases at the same loading cycles. Due to the inhomogeneous distribution of particles with different sizes, the velocity and displacement of the sample vary in different directions, exhibiting mesoscopic anisotropy. The contact force is relatively even in the downward direction while dispersed near the edge of the sample. This means that the particles at the bottom are less affected by loads and the internal evolution of soil samples conforms to its macroscopic deformation behavior during cyclic loading.

In order to study the creep characteristics of the coarse-grained soil as embankment filler under long-term vehicle loading, the creep test was performed on coarse-grained soil using the large scale dynamic and static triaxial instruments, and the creep process of the coarse-grained soil sample was simulated by PFC3D software, and the internal particle motion and energy change during the deformation process were studied. The research results show that the coarse-grained soil embankment filler has non-linear creep characteristics. At a low stress level, the coarse-grained soil is in the stage of elastic deformation. At a high stress level, the final creep deformation curve of the coarse-grained soil does not converge. The creep process is a process in which the particles are distorted and rotated, changing from an unstable state to a stable state. During this process, the particle energy is dissipated to the minimum, and the creep of the sample reaches a stable state. This understanding of particle motion and energy changes during the triaxial creep test of coarse-grained soil will help deepen the understanding of creep characteristics of coarse-grained soil and provide a reference for engineering practice.

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Split Hopkinson pressure bar technique has been widely used to measure the dynamic tensile strength of concrete materials. Most experimental results show that the tensile strength of concrete material increases with strain rates. However, the dynamic tensile strength derived from the split Hopkinson pressure bar test is affected by lateral inertia confinement, which may lead to the overestimation of dynamic mechanical properties of concrete materials. The true dynamic characteristics of concrete materials are not actually shown by experimental data. It is impossible to completely eliminate the influence of lateral inertia confinement in split Hopkinson pressure bar tests. In this study, a rate-insensitive material model is used in commercial finite element software to study how the lateral inertia confinement affects the dynamic tensile strength of concrete material at strain rates between 30/s and 150/s. Comparison of finite element results and split Hopkinson pressure bar test results shows that the dynamic tensile strength enhancement of concrete materials is strongly influenced by the inertial effect. The dynamic increase factor of concrete materials which remove the influence of lateral inertia confinement in split Hopkinson pressure bar tests can reflect the true dynamic characteristics of concrete materials. It is also found that the influence of lateral inertia confinement is related to the size of the specimen.

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