Stress-dilatancy behaviour of fouled ballast: experiments and DEM modelling

• Published in: Granular matter Vol. 23; no. 4
• Main Authors: Chen, Jing, Indraratna, Buddhima, Vinod, Jayan S., Ngo, Ngoc Trung, Gao, Rui, Liu, Yangzepeng
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2021; Springer Nature B.V
• Subjects: Clay; Coal; Complex Fluids and Microfluidics; Contact force; Contact stresses; Coordination numbers; Dilatancy; Dilation; Discrete element method; Engineering Fluid Dynamics; Engineering Thermodynamics; Fouling; Foundations; Geoengineering; Heat and Mass Transfer; Hydraulics; Industrial Chemistry/Chemical Engineering; Materials Science; Mechanical properties; Numerical prediction; Original Paper; Physics; Physics and Astronomy; Rotation; Shear strength; Shear stress; Shear tests; Shearing; Soft and Granular Matter; Direct shear test; Fouling; Discrete element method; Coal; Stress-dilatancy relationship; Clay fines
• ISSN: 1434-5021; 1434-7636
• DOI: 10.1007/s10035-021-01150-1

This paper presents a study of the mechanical behaviour of ballast contaminated by different fouling agents such as coal and subgrade clay. Large-scale direct shear tests were carried out to examine the strength and deformation properties for coal-fouled and clay-fouled ballast. The experimental results show that fouled ballast (both clay and coal) exhibits a lower peak shear strength and decreased dilation during shearing. The clay-fouled ballast shows higher shear strength and smaller dilation compared to coal-fouled ballast. The relationship between shear stress and dilatancy of ballast under different fouling conditions is reported in this paper, where the numerical predictions are made using the discrete element method (DEM). The DEM simulations show that with the increase of fouling level, the coordination number, the average contact force, the particle rotation and the velocity decrease for ballast aggregates. The results indicate that coal-fouled ballast exhibits a smaller average contact forces with less stress concentrations, less major principal stress orientation and a greater coordination number, leading to less particle rotation and velocity compared to those of clay-fouled ballast for the same degree of fouling. Graphic abstract