Numerical modelling of tyre-derived geo-composites

Abstract

This thesis aims to study the property of rubber–sand mixtures as a geotechnical alternative. Previous studies have shown superior properties of this artificial composite such as high resiliency, light weight, and improved skin-resistance. Also, when mixed with conventional geotechnical materials, the composite often exhibits adjusted void ratio, high compressibility, high compression, high friction angle, and high attenuation of vibration. In the past, the major efforts were focused on the laboratory tests. There is limited research in numerical domain performed to predict the mechanical behaviour of rubber–soil. In these numerical studies, approximations are unsatisfactory because the past studies usually treat the compressible rubble granule as a rigid material. To address these research gaps, this study in this thesis develops and applies a series of numerical models to replicate the compressible nature of the rubber material and to examine the behaviour of the rubber-derived composite materials. The behaviour includes the shear strength, dynamic damping, mixture segregation, contact asperity, and contact deformation, from the macro-to microscale. The aims of this thesis contain the following aspects: 1) investigating the shear strength of rubber–sand mixture obtained in direct shear test; 2) assessing the segregation occurred when rubber–sand mixture is placed; 3) developing a coupled numerical method to replicate rigid–soft matters interaction; and 4) examining the influence of material surface asperity on energy dissipation. To attain these aims, the discrete element method (DEM), a numerical modelling tool, is employed to develop a series of modelling framework. The framework is validated, verified and applied through a blend of solutions, including test setups, analytical solutions, example problems and case studies. The DEM is used to replicate the discrete natural of rubber granules. Using this method, the macroscopic material response and particle flow can be monitored by determining granular properties such as contact stiffness, friction and damping coefficient. As a significant numerical tool, the commercial software package PFC is used to investigate the rubber and soil granular interactions.