Influence of Particle Orientation on the Performance of Geogrid Reinforced Ballast

Jian-Bin Zhao,Chen-Xi Miao,Jun Zhang,Jie Li,Xiao-Hong Bai,Giorgio Pia

doi:10.1155/2020/6758059

Abstract

To explore the initial orientation effect of ballast assembly on the reinforcement performance of the geogrid reinforced ballast, particles with random orientation and five prescribed rotational orientations were developed through particle flow code (PFC3D). The evolution laws of the pullout force and the principal directions of the normal contact force were systematically compared and analyzed. Furthermore, the mechanical responses such as pullout force, distribution of axial force, displacement vectors, force chain, and mesoscopic fabric were discussed. According to the displacement vectors of the ballast particles, the average thickness of the stable shear band is determined. The inherent relationships among the force chain, the rotational angle of the normal contact force, and the mesoscopic fabric parameters are revealed. The results show that the pullout force of specimens with the initial orientation of 45° increases monotonously during the pullout process, and the peak value of pullout force appears at the end of the test. The mesostructural analysis also confirms that the evolution of the principal direction of contact normal force is relatively steady during the pullout process, indicating that the specimen with 45° orientation possesses higher systematic stability and ductility. Moreover, the optimum interval from 56.68° to 57.30° is observed to remain in a self-adapting state for ballast assembly.

Highlights

Compared with the considerable compressive strength, the tensile strength of soil is nearly negligible, especially for coarse aggregates
The microfabric, displacement vectors, axial force of geogrid, segmental strain, and force chain are analyzed, and the evolution law of pullout force and the principal directions of normal contact force anisotropy are compared with different initial orientations, which provides a certain reference for improving the performance of geogrid reinforced ballast from the perspective of particle arrangement
A numerical model using PFC3D is established to reproduce the pullout behavior of the triaxial geogrid embedded in ballast aggregates, and the influence of the initial orientation of ballast assembly with the angles of 0°, 30°, 45°, 60°, 90° and random orientation on the geogridballast interface strength are explored from the macro and micro-perspectives

Summary

Introduction

Compared with the considerable compressive strength, the tensile strength of soil is nearly negligible, especially for coarse aggregates. Laboratory pullout tests can reflect the evolution laws of reinforced structure splendidly but fail to clearly reveal the distribution mechanism of geogrid-soil interface force and the transfer mode of axial force of geogrid [12,13,14]. To bridge the gap in laboratory pullout tests, the macroscopic and microscopic characteristics of the geogrid-soil interface have been studied by plenty of scholars in numerical simulation. The microfabric, displacement vectors, axial force of geogrid, segmental strain, and force chain are analyzed, and the evolution law of pullout force and the principal directions of normal contact force anisotropy are compared with different initial orientations, which provides a certain reference for improving the performance of geogrid reinforced ballast from the perspective of particle arrangement

DEM Modeling

Influence of Particle Orientation

Conclusion