Investigation into the mechanical behaviour of bio-cemented sands using the discrete element method

Bio-mediated methods, such as microbially induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP), have gained considerable attention as alternatives to invasive ground improvement techniques. MICP and EICP use biogeochemical processes to drive carbonate precipitation and bind soil grains, thereby improving the...

Hydrodynamics of expanded bed adsorption studied through CFD-DEM

The hydrodynamics of the Expanded Bed Adsorption process is studied through simulations combining Computational Fluid Dynamics and the Discrete Element Method. A representative base case is defined, based on process design parameters commonly encountered in literature. Then, 19 other cases are defined, each representing a singular adjustment...

A coupled MPM-DEM method for modelling soil-rock mixtures

Aiming at modelling the mechanical behaviour of soil-rock mixtures accurately and efficiently, a coupled MPM-DEM formulation combining the material point method (MPM) and the discrete element method (DEM) is proposed. It is solved concurrently via the contact force linking the two individual methods. Specifically, the soil is modelled with...

Effects of carbonate distribution pattern on the mechanical behaviour of bio-cemented sands: A DEM study

Microbially induced carbonate precipitation is a promising ground improvement technique which can enhance the mechanical properties of soils through the precipitation of calcium carbonate. Experimental evidences indicate that the precipitated carbonate can display different distribution patterns. Crystals can develop at grain–grain contacts ...

Experimental study and discrete element analysis on lateral resistance of windblown sand railway

The lateral resistance of ballast bed is an important parameter to prevent track expansion and maintain track stability. The invasion of sand particles can cause the change of lateral resistance of ballast bed and affect the stability of track structure, but little attention has been paid to the change characteristics of nonlinear lateral...

Structural analysis and parametric study ballasted track in sandy regions

The sand intrusion in railway tracks in sandy regions can significantly change the mechanical behaviour of tracks and thus threaten the safety of train operation. This paper presents substantial field tests on both sandy and clean railway tracks to study the effect of sand intrusion on the longitudinal resistance of ballast bed and the...

Numerical analysis of train-track-subgrade dynamic performance with crumb rubber in ballast layer

Crumb rubber (CR) has been proposed to apply in the ballast or sub-ballast layer for ballast degradation mitigation and vibration (noise) reduction. The CR can change the ballast layer stiffness, which can affect the train-track-subgrade dynamic performance and cause travel comfort and safety issues. Towards this, this study aims at...

Analysis of Railway Ballasted Track Stiffness and Behavior with a Hybrid Discrete-Continuum Approach

Railway ballasted track stiffness is an important indicator to identify supporting condition that ensures that the facility is well designed and functioned. Although many studies have been performed on track stiffness based on experimental tests and finite-element methods, the factors influencing the track stiffness have not been completely...

Experimental and numerical study on lateral resistance of frictional sleeper with arrowhead groove

To enhance the stability of continuous welded rail (CWR) tracks, frictional sleepers have been developed. The frictional sleepers are new types of sleepers with grooves on the bottom, and different bottom grooves improve lateral resistances at different magnitudes. In this study, single sleeper push test (SSPT) and its model with discrete...

Rheology study of ballast-sleeper interaction with particle image Velocimetry (PIV) and discrete element modelling (DEM)

Ballast rheology is a phenomenon that describes movements of ballast particles due to the discrete nature, which eventually leads to the ballast bed fluid deformation after a long-time service. In most cases, ballast rheology is the main reason of track irregularity that leads to some track defects, e.g., hanging sleeper and mud spots....

Optimization of a convex pattern surface for sliding wear reduction based on a definitive screening design and discrete element method

A previous study revealed that a convex pattern surface can reduce sliding wear of a transfer chute. A convex pattern surface is a flat surface outfitted with a pattern of convexes defined by five parameters. A three-level definitive screening design (DSD) method combined with discrete element method (DEM) is used to investigate the influence...

Calibration for discrete element modelling of railway ballast: A review

The discrete element method (DEM) has been confirmed as an effective numerical method for modelling railway ballast, and successfully used to analyse a wide range of ballast-related applications (e.g. geomaterials). However, there still exists some aspects under development. Among them, the model calibration can be the most significant one ...

Macro-meso dynamic analysis of railway transition zone: Hybrid DEM/FDM simulation and experimental validation

To probe into the mechanical behaviour of railway transition zone from the macro-meso aspects, a numerical model of transition zone is built that hybrids the Discrete Element Method (DEM) and Finite Difference Method (FDM). The DEM is utilised to simulate the ballast bed and sleeper, because it can consider the realistic ballast shapes and...

Breakage behavior of biomass pellets: An experimental and numerical study

The presence and generation of fines and dust in the bulk of biomass pellets have inflicted several problems in the supply chain during transportation and storage, and the breakage behavior of pellets has been scarcely studied so far. Fines and dust are the consequences of impact and abrasive forces through the whole supply chain; however, the...

DEM modelling for flow of cohesive lignocellulosic biomass powders: Model calibration using bulk tests

Biomass feeding problems greatly hinder the industrialization of entrained-flow gasification systems for production of 2nd generation biofuels. Appropriate DEM modelling could allow engineers to design solutions that overcome these flow problems. This work shows the application of a DEM calibration framework to produce a realistic, calibrated...

Lateral resistance of polyurethane-reinforced ballast with the application of new bonding schemes: Laboratory tests and discrete element simulations

To mitigate the ballast flight risk in the high-speed railway, this paper presents three new polyurethane bonding schemes which have negligible influence to tamping operations. With the application of these bonding schemes, a series of laboratory tests indicated that the polyurethane-reinforced ballast exhibited much larger lateral resistance...

Experimental and numerical investigations on the shear behaviour of recycled railway ballast

Ballast degradation is frequently observed under cyclic loading, and results in bearing capacity and drainage problem of ballast track. To keep the stability and safety, periodical maintenances are needed, such as cleaning and replacement, which produce a huge amount of wasted ballast. Thus, reusing the deteriorated ballast can become a...

A granular Discrete Element Method for arbitrary convex particle shapes: Method and packing generation

A novel granular discrete element method (DEM) is introduced to simulate mixtures of particles of any convex shape. To quickly identify pairs of particles in contact, the method first uses a broad-phase and a narrow-phase contact detection strategy. After this, a contact resolution phase finds the contact normal and penetration depth. A new...